I looked back over your many prior posts, and I remember the history of having a pretty negative role model in the house - your boyfriend was not a good influence on your son. It took you a long time to get rid of the boyfriend, and it's good that you did. But the effects on your son will take more than a few months to erase. If he can be with his father and perhaps have more structure (or even a different environment) for a while, that may very well be a good thing. Teens often get mad and stay mad - so you have to be the adult here and be much more patient with your son while he works through all these conflicting feelings. He has a drug problem and a defiance problem, and I hope his father will get him into therapy and make him attend. Be grateful that your son's father is willing to step up, and let him carry the load for a while.
Meantime, please work on yourself through counseling. You have made a tough decision, and difficult as it is, continuing the way you two were going was not a good option. It's fine to let the other parent take over for a while.But you also have a long history of not being sure of yourself and not being able to make tough decisions, so this is the time to work on strengthening your own resolve and becoming more self-assured and more confident.
I think it's unrealistic to expect your son to call. He does not "owe" you a phone call. He's adjusting, he's hopefully dealing with more discipline, and he has a whole new house and school situation to deal with. It's great that his dad is communicating with you. I think you can drop your son a card or note now and then just to say you are thinking of him and that you love him forever. Please don't put in anything about doubting your decision! Discuss that with your counselor, but don't share adult issues with a teen, particularly a vulnerable one who is struggling with drug and other issues. Don't ask him to make you feel better - you don't give a child the job of helping an adult. Just assure him that you know he's a wonderful kid inside and you know that, with time and work, he will get himself more on track every day. You can tell him you miss him, but don't go on and on about being miserable, you know? You can work on the dos and don'ts with your counselor, and perhaps in consultation with your son's father and your son's therapist.
As B said, make this the time to focus on YOU. Do NOT get into another relationship until you get yourself straightened out.