Yes, you have remained calm and controlled and I'm so glad for you, if you hadn't I think you probably would have been even more hurt because this guy is obviously either really narcissistic and/or vicious or he's just really messed up.
Now, relationships end all the time, but the reason I say that is because of your story. Years of talking to him while he is in jail, his promises and the story he wove. Then he gets released, immediately comes to you then disappears - tell you he loves you.
So yes, either vicious or narcissistic or very messed up.
The thing is though, regardless of the WHY, you are well to keep your distance.
I remember reading a thread in F&F one time and basically the person was appalled that an alcoholic, with no job etc (I forget the details) who she had been nothing but supportive to, dumped her!
I hate that term, dumped btw, but that was the post.
Anyway, someone said, had it occurred to her that if she was on his wavelength (ie drinking and partying), perhaps they would still be together.
Is that not the way you see your situation? You spend months talking with him about his new upcoming sober life, you make plans, you plan on taking it slow etc etc. Then he gets out and thinks Hell No! I want to drug and party. Now where on earth would you fit in to that? He may well love you, but you don't fit in with his addiction at all, you are the person who just discussed his new sober life!
So he ran away from that, not from you personally - from that life, it's not what he wants, he wants drugs/alcohol and that's not you.
It's not personal, it's not that you aren't good enough it's not that he may not love you as much as he is capable of, but his first choice is his DOC and I know you must know enough about addiction to know that always comes first.
Anyway, that's just my take on it.
And yes, it' hurts you anyway and I'm sorry about that. It will get better with time.