you left because you wanted some sanity. you wanted to protect your tender son, and yourself, from the world of hurt that was waiting for you in your own home.
now your husband has had a moment of clarity. but i think that if too much is handed him, in the way of assistance, greasing the skids for his new life, that it just backfires. it's not scientific, or anything i can even articulate very well, but i've seen that happen more than once - it's like the consequences of their actions -- if they weren't painful enough to really change their life, they don't really change their life.
hands off. keep building your safe life with your son. perhaps he will turn things around and then you can think about being a family again. it sounds like he wanted to do a little something when you first moved, now he realizes he needs to do a little more. but the reality is he needs to do a lot more.