Well, i can honestly claim i read all of that. Your story (your dramatized version anyways) is alarming. From my INTJ perspective, i can tell you (in a logical and reasonable manner, unlike your boyfriend who is experiencing internal chaos) that the relationship is over. He has lost his trust of you (and this can probably never be regained...reasons i shall give below). The only reason he is clinging to what is left over in the relationship is b/c he is unwilling to let go of what "was". He doesnt want to be alone again and lose what he once believed was "perfect". But deep down, he is convincing himself (as we speak) that it is over. The only way this may not happen is if he is really desperate (as defined by INTJs themselves).
Why can the trust never be regained?
Its because he trusted you more than anyone else in the world. He doesnt have very many friends and he doesnt want very many. He put all his trust in you and all his energy for you. When he found out that you are a girl who sleeps around with her friends for whatever reason you do, it probably disgusted him deep down. I am pretty sure that he doesnt sleep with any of his friends, so it does bother him. Few months back, he didn't want to lose what he considered most precious, so he let go of it, even though, deep down he lost that strong initial trust in you.
Now that he doubts you again, i would say that even if somehow you two stay together, he doesnt trust you...not in the way he wishes he could and in the way you wish he would.
So whose fault is it? In my unbiased perspective (if i can so convince myself as well), it is your fault. You should have known better than to hang out with some other friend and lie about it. Now he believes you to be a liar (he probably already knew you to be a liar, since ENFPs aren't known to be the most honest of all types), but now even more so...he just cant trust you anymore. I doubt your relationship can last. Just saying how i see it.