Hi Izzy,
I've followed your story for a few months now and I really hear the anxiety and stress this relationship has caused you. My heart goes out to you.
Just friendship steelwork; but without all the drama which I know is a massive ask and very unlikely. If he could communicate better and tell me I'm doing his head in rather than cut me off I would respect it and give him the space he needs.
I'd just like to point out that this isn't a big ask. It's a question of basic respect. Yes, it might be hard for him because he likely has a turbulent inner emotional world. But I doubt you do him or yourself any favours by signalling that you don't expect simple respect and decency from him. It sounds to me like you have tried walking on eggshells around him and that he has shown little regard for you when he simply cuts communication. Do you really think walking even more gingerly on the proverbial eggshells will be the solution?
I'm not sure what my expectations are but just hope maybe I can manage the push/pull better and be more meh if and when it happens again.
What if you tried telling him openly, calmly, but firmly that you care for him and for his friendship, but would like to see some recognition on his part of the pain he causes when he simply disappears and, more important, some effort to work on that?
It's madness as we are only friends and friends shouldn't be this complicated or stressful. But then it's mental illness at play isn't it.
In my humble opinion, healthy compassion means understanding why he might act the way he does and accepting that he might not be able to change. But it does not mean making excuses for him and letting yourself be treated with disrespect or little to no regard. If you asking to be treated with respect is a deal-breaker for him, why isn't that a deal-breaker for you?
I hope these questions aren't too blunt. I remember the pain you expressed after the last time he shut you out and it sounds like you still blame yourself and are vowing to take on even more blame and walking on eggshells this time around. Take the time to think it through, as others have said, so that you don't set yourself up for a possibly more painful discard.