Also bipolar here, and I could not agree more. Also, his feelings for you turning on a dime are NOT a symptom of bipolar. He has other issues. And you mention being afraid to "leave" him for fear he'll kill himself. I hardly know where to start with why you should not let this interfere with doing what is best for you, but please think how easy it would be for him to pretend such a thing from online! Hell, he could totally do it (pretend) for no other reason than to manipulate you! In fact, if he's threatened it at all, it is VERY likely he would do such a thing (manipulate you by pretending). Even short of that, what about scaring you with spells of non-response? Do you really need that? With the abandonment issues you have? No!

THIS. He could be ANYBODY. I've personally encountered someone who pretended to be dying and had all kinds of people fooled. It was total BS. And those people also would say what a "nice" guy he was.

Don't kid yourself -- you are in a "relationship" with a projection.

Sorry if that comes off harshly. But I really believe you are setting yourself up for a disasterous fall if you don't cut him off. Completely. Because if you, as you put it, have a savior complex, he will just keep sucking you in over and over again.