Flygirl, I am so sorry. And I hope you continue to go to al-anon, get real-life support and of course continue to read and post here too. The what-ifs.... I hope you realize that there was nothing you could have done to stop him. I have had close friends lose loved ones to suicide and they keep going over everything again and again, and I tell them the same thing... you can't put rational thought around irrational behavior.
I am so sorry for your loss, know that he is finally at peace. Hugs to you.