1. did i do the right thing by totally disengaging? am i to help in any way or just let it go? You did the right thing. Let it go.
2. why was i jealous when gary mentioned that nathan's car is at some girl's place from the sober living house, even when i know that i cannot and do not want to be with him? Because you haven't yet fully detached. It takes time, but you are making good progress.
3. he is drinking at least a bottle of vodka a day. is he going to die soon? That's up to him.
4. if an alcoholic is in the middle of his self destruction, is calling an ambulance the way to go in the first place if he is not or cannot even really ask for help? If he is a danger to himself or others, yes.