sorry that you are in so much pain, it does get better. at least you sound like you know what you don't want. maybe you could do what you can to keep your mind occupied, try changing those thoughts if you find yourself obsessing.
i have been where you are more times than i can count, and you don't have anything to feel bad about. what you feel, i think, would be normal for any breakup, besides he hasn't been gone that long, even though i know that it feels like eternity. this could be the break that you both need, for him to reach his bottom and for you to find you.
i found it easier for me if i didn't futurize or finalize anything in my own mind at first. try to allow time to help you decide when to do that. maybe not look at it like a forever thing, maybe just a one day a time thing. try not to think about what might happen tommorrow at all, stay in the day. it helped me a lot. futurizing makes it feel like a death or something. when my ah would have to leave, i would talk to him went i could and felt strong enough and when i couldn't i didn't. i don't think there is nothing wrong in telling him how you feel, its what you do after you let him know how you feel
in my opinion, i don't think that you have heard the last of him, so if i may, i suggest that you dive deeper into your recovery, go to more meeting so as to get yourself prepared for more of his promises. don't get caught off guard. keeping you and yours in my prayers