He has the tools he needs, jc. You can be encouraging in your words, you can pray that he absorbs the vast benefits AA has to offer, and you can hope he will make the right choices for himself.
Aside from that, it's his battle to fight, not yours. He knows you care about him, he has tools to stay sober......now all he has to do is keep working a program of recovery. Does he want to go to a sober house? Would it help? If his home environment truly is triggering him, I would not be above pointing him to some appropriate resources and letting him make arrangements for that.
I know it's sometimes very hard to stand by and let him sink or swim, but in this case it's really your only choice. Wishing you well!