Fast shot seems like it needs to do something in case the model does not have an increased attack characteristic. It's the only advance that demands that you've gotten another specific advance, and a relatively rare one at that. I've used these rules in three campaigns now, and rolling up Fast shot is considered to basically be the same as to roll a blank. I've gotten this skill on someone in every campaign, but it's never been used.
I think it would be better if you got one additional shot for each attack characteristic. So you got (1+A) number of shots, instead of just (A). Then it wouldn't be a total waste. Perhaps balance it by giving a -1 to hit for each consecutive shot?
Or maybe just allow people to reroll this skill if they don't have any attack characteristic increases?
I mean, it doesn't make much sense as-is. "Hey, look at me. I'm a fast shot, in the time it takes anyone else to shoot one shot I can shoot... uhm... one."
Also, if you already cause Fear from one source, say scars, Killer Reputation does nothing. I can understand this, in a way, but it's another one of those situations where the player has spent an effort to gain a rare advance for his guy, manages to get a skill and is rewarded with absolutely nothing. Maybe they should stack somehow? Terror?

Chemist - Very, very weak skill. First there's a 1/6 chance that anything happens at all, and all the results are very cheap and on top of this you can get addicted. To a drug that you have 1/36 to be able to get a hold of again. Could maybe work as the drug dealer contact. Once the chemist has made a dose of the stuff the gang can buy one dose of the drug in subsequent post-battle phases where he didn't go OOA, the cost representing the cost of the chemicals?
Disarm - Is the point really to destroy valuable shooting weapons? Because that's all the skill has accomplished in my games. Charge the specialists, instantly destroy/disable that pesky plasmacannon. Either the weapon should not be permanently lost, or this should only be usable on weapons used in CC.
Other than that, these skills are very good.