Apologies for the late reply, but I've been very busy of late. I'm also not an expert on Ratskins, and haven't faced them much since 1st Edition, which was the superior edition anyway.
Firstly, I'll reply to some of your comments, and see if I can offer any additional suggestions (it's worth noting if you want a quicker response or in-depth discussion, PM me and I'll give you my email - if it's not already in my sig... can't remember...).
well, one of my key goals was to make sure these wouldn't be excessively common. i'm actually a little bit concerned that some of them are too much (for example, getting a new territory roughly every 6 games on average is not a huge deal for a house gang usually, but getting a 120 or 240 credit windfall can *really* change things for an outlaw gang.
This is true, and I certainly think it's worth being concerned by exactly how much credits any outlander gang gets. I should mention that although the chosen skill selection
seems rare, in my experience it isn't quite as rare during advance rolls as it seems statistically. Certainly I think you'd need to heavily tone down quite how much Credits an Outlaw gang can get through skills, as this does give them a pretty unfair advantage over other Outlanders. Outlander Gangs should be (with the exception of Spyrers and Enforcers) struggling for cash all of the time. It is part of the experience, and there isn't supposed to be an easy solution.
tech savvy - well... the chief can use grenades and ammo. i halfway suspect that they should all be able to use grenades and ammo, and it was left off by accident (though i certainly can't offer any proof). and being able to use power weapons (or rather, all melee weapons in general) just makes sense to me as well; they can use lasguns, but not a power axe? about the only iffy part imo is the pistols, and most of them aren't so good anyways. and the good ones? well, they have no way of getting those directly. they don't show up on the outlaw trading post chart. so, if the rules were changed such that any member of the tribe can use the weapons and ammo (and probably remove bolt ammo from their list, so they have to give up a rare trade), i wouldn't feel this was really needed. honestly, the main reason for the other stuff is that it felt they should have the grenades and ammo to begin with... the rest sorta... just... got added because i felt like i was giving them stuff they should have already had.
Hmm I'm not sure about that, to be honest. In the 1st Ed Ratskin rules, only Chiefs and Shamans could have grenades and ammo. All House Basic weapons were "special" and could not be used by Braves. That has essentially not changed, and for the most part I feel that is correct. A while back, this was heavily debated by the answer mods and necrotesters; concerning weapons advancement through a campaign. It is a complex issue, but I think limiting it to just pistols and close combat weapons in this case is a reasonable compromise, but I still see it as Techno Envy
sniper - bearing in mind i presume they should all be *allowed* to use grenades and ammo, they should pretty much all be able to use a boltgun as well (since it's not that different from a shotgun with bolt ammo). hunting rifles i feel fit in well with the tribe anyways (and honestly, should probably be added to their list in the first place without any skill required, imo - in fact, the ratksin scout hireling in the CE rules can use one). storm bolter and needle rifle might be a bit excessive, i guess. on the other hand, it's a tiny fraction of a specialist, and both are rare rolls that don't actually appear on the table the ratskins roll on... these things are more likely to be trophies of battle than anything. i don't see a problem with letting them make use of those options if they should find them, and frankly it was one of the skills i was least worried about. plus, remember, it's not a skill category the ratskins actually get, it's a skill category they can take only when they roll a 2 or a 12. still, would it make you feel better if it was changed to be hunting rifle only, and they gain the shooting skill category (as a replacement for their combat skill category)?
Once again, I disagree on the shells and grenades. I thought like you it might be an oversight, until I checked my old hardback, and noticed even then regular ratskins couldn't get them. IMO, this makes sense, as a Chief will usually get the best equipment. Still, a individual Ratskin might be able to prove himself later on to carry grenades and ammo, and such. However, this is not a mistake in the rules, this is how it has always been for the Ratskins.
As to Sniper, well I agree that the Hunting Rifle makes sense, and well, the Needle Rifle would be so utterly rare as to be not an overpowered consideration. The Storm Bolter imo, is just many shades of wrong. I don't even know where the rules of it come from (must be Ash Wastes or something), but that's just too much. I'd stick the regular Bolter into this entry. I'm not a huge fan of Ratskins running around with Bolters, but imo a Sniper would have it, if any. I'd remove the Storm Bolter and replace it with a regular bolter, and you're set imo. The Storm Bolter is too outside of the regular Necro rules to make much sense, imo. Sure the Hunting Rifle is a AW Nomad weapon if memory serves, but it should be in the normal rules imo.
i do have to say, i find it ironic that some of the abilities i was most worried about getting lambasted are the ones you are the most accepting of 
I'm not a good representation of gamers in general to be honest. But I like fluff, and its the fluffy entries that I like the most. If one is going to do a new skill table exclusively for a faction, it should represent what they are like!
i've been really worrying that some of the skills are handing out a bit too much to the ratskins, especially when you consider that all their income goes directly to their stash.
Yeah, that is a pretty big concern, especially with not having the Income Tax House Gangs get. I still think you're heading in the right direction with these skills, they just need some playtesting and balancing and you're set.
weapon expert - i really do feel this is a good skill. as it stands, it's pretty much best to completely ignore the existence of the primitive weapons and just use a mixture of whatever you can get... with braves costing an extra 10 credits, coming with a free club (and knife, afaict), and not getting an extra advance over a ratskin, i just don't see much need to ever use these weapons. i really feel it would add quite a bit to the gang if at least one or two warriors could use these weapons and still be at least a bit effective.
Umm... Braves are like Juves... they slightly more than half the cost of a Ratskin, meaning you can take a decent amount of these with Blundabusses and muskets, and have a cheap amount of ranged sniping and close range pinning inducers on a very low budget. They cost more than a Juve should, but it is the same for Ratskins, who are also 10 more points than a ganger should be, and this cost factors in their additional rules, one of which being their injury ability, making them very tough to actually kill. Plus, later on in the game one would assume that Braves become regular Ratskins, and thus have access to the Special Weapons category.
I like this skill because it encourages the Ratskin player to use primitive weapons. Although a Ratskin gang will expand its weapons over time, do remember that Ratskins observe a tradition which makes them heftily shun the ways of the Hivers, meaning a few of them would want to avoid weapons used by Hivers. In short, its nice that this skill table can provide both options. There is certainly an argument that you should be ignoring weapon restrictions for all gangs late campaign anyway.
mapmaker - ok, about what i thought.
explorer - still a little worried about getting that large income increase
forager - was kinda worried it might need a downgrade, actually...
My only issue with Mapmaker is that now that I've read up on Ratskins, this gives them a pretty unbelievably huge advantage when selecting scenarios, as the Ratskins already get bonuses to the scenario table. This means you could be adding or subtracting 3 from the roll for Scenarios, making this a pretty massive advantage, and you'll probably be able to actually choose more or less any scenario if you roll a 3 or 4. Factor in the source of income as well, and that's a pretty powerful skill. It might be worth considering limiting this skill to one of those two bonuses, as the inherent Scenarios rule Ratskins get suggests they at least are
using Ratskin Maps. I still do like this skill, but playtesting will be required with it for sure.
With Explorer, indeed, this does need fiddling with. My main point was more that this represents Ratskins better, imo, than whether or not the income is an issue, as it is. The best way to tone it down is to make the skill difficult to pull off, so you'd forgo foraging
and require a 6 to find one (or you're making a table where on a 1 you lose that Ratskin, 2-5 you find nothing, but perhaps scavenge some credits on the way, and on a 6 succeed). Besides, its clear you're rolling on the House Gang Territory table, something no Outlaw should have access to anyway. I know the idea is to get a chance of getting more Archeotek Hordes, but it needs to be severely limited, otherwise foraging becomes completely pointless, and Ratskin Foraging is already better than other Outlaws (only Ratskins get that +1 to foraging).
Thus we get to Forager. On second thoughts you're right about that downgrade. 2D6+1 imo would be about the highest I think you could potentially get away with. The other alternative is merely allowing this skill to be cumulative, but subsequent skills merely add another +1, rather than an extra D6.
Sorry this reply has taken too long. Much has been happening in RL recently.
