UGH. i am so sorry you have so much insanity to deal with. i'm glad you had some good time with the step-D, that poor kid.
your AH is being a complete self-absorbed jackass. you did the right thing, the ONLY thing....refusing him access to the house and kids if he's going to get high. his mind is far far away from the life right in front of him. now seeking other ways to get high - synthetic pot has been around and it's nothing to mess with. but he's turned into a "more" monster.
it's ok to be angry. VERY angry. not all of his actions can just be written off to the disease. and he "could" be taking steps NOW to deal.
so i guess plan B and maybe C remain in place? even IF he gets on the plane, that is no guarantee he's going to get into recovery and stay there. even IF he completes treatment, coming right back home is probably not the best idea. he has some "proving" to do. in my opinion anyways....
does he have his suitcase and plane ticket?