You might like to read about limerance. I found it a useful concept as part of trying to understand some of the less healthy feelings I have experienced around men and relationships.
en.wikipedia.org/wiki/Limerence
There can be an incredibly intense experience around meeting someone new. He’s been chatting to you frequently and in between you’ve been thinking about him all the time and building it up in your mind.
And now there’s a major bump in the road and you’re confused because his behaviour doesn’t fit with the expectations you had built up.
I can’t guess at why he has done this, but you are now feeling overwhelming grief because the intense experience you had and the expectations you built around it are breaking or gone. That’s why it hurts so much. It was in your mind all the time before, and now it is still in your mind all the time, but the feelings are negative rather than positive.
That feeling of falling in love (or limerance, if that term clicks for you) is wonderful and near to addictive. Having experienced it once in adulthood and then having got past it (like you, with great pain) I recently found myself falling again, but this time had control over the feeling. I could actually examine the way my mind wanted to flow and could to a large extent switch it off, if I chose as I could see when I looked at it logically that it didn’t make much rational sense.
That way it felt in my control and I was able to enjoy the feeling while knowing that if it didn’t work out, I had hadn’t let myself give my entire being over to it.
I said I couldn’t guess why he has done this, but looking back at my own experience, I think the man I fell for couldn’t bear the intensity of the feeling and so backed off as soon as it all got too close. He had long term MH problems as well. I wasted a lot of time hoping he would get over it, but I don’t think he was capable and he was a similar age and demographic to the man you’ve described.
My advice, for what it’s worth, is to try to keep busy with other things and whenever the thoughts of him slide into your mind, shove them aside and don’t let yourself ruminate. Others have suggested giving him a chance and if you do, set careful boundaries for yourself and stick to them so that if you find he is running hot and cold, you need to be the one to put a firm end to it and cut all ties entirely. It’s the only way to put it behind you.
Sorry you’re going through this and good luck.