TW, I'm one of those who handled divorce on their own, using a lawyer just for consult to make sure I understood things and filled them out correctly and on time. In my case, we spent about 15 minutes in front of the judge and it was all done.
Now granted, I had a cooperative husband, no debt, no kids, no joint investments, and he did not fight me for the house, which I brought to the marriage. However, I think that what others say is right, you should at least consult w/an attorney--it sounds like you really have nothing to lose, and since you don't own much in common, the kids are the only issue.
Another thing I've heard said here a lot is to document, document, document about your AH's behavior. Losing his job, not showing up to pick up kids when he's supposed to, getting beat up in cracktown, anything else that will show his pattern of substance abuse, lack of financial responsibility, etc. All that will go towards your desire for sole custody of the kids.
I'd also like to echo what Wisconsin said about divorcing as a way to protect yourself from potential fallout should he get in a car accident or otherwise hurt or kill someone. This was also a factor for me in deciding to divorce--XAH has a pattern of driving drunk and eventually he'll either be stopped for DWI (roughly $10K in costs) or he'll get in an accident. I didn't want to be part of the liability for either one of those.
If you look up some of my recent posts, you'll see that he did in fact have an accident (not driving related) that has resulted in him being out of work, living on disability until/if he can return to his old job, and looking at the costs for an ER visit, surgery, and 2-1/2 days in the hospital. (Yes, he luckily has insurance, but that is going to be one hefty bill to pay the deductible and 20% of). I am thanking my lucky stars that none of this is my problem. Protecting yourself and your kids from a similar situation just makes sense.