This now seems delusional
Can I suggest you pause right there, before you head off in that direction?
I know your life has had more than it's fair share of toxic relationships. YOU have not caused them. I'm willing to entertain the idea that you might have some kind of role in attracting the wrong sorts of people. Not because that's what you actually want (much less is it something you deserve!). Just that, not realizing what we're doing, we sometimes mess this stuff up. You're making progress here, really you are!
So, he could actually have some sort of mental disorder. Probably not? My T says that someone can be overly self involved without crossing the line into narcissist, for example.
What you DO know. 1) He's self involved. 2) He apparently has a lot of self worth. I'm saying that because he seems pretty convinced that there's no WAY you could not want a relationship with HIM. 3) He's not much on taking "No" for an answer. 4) Some or all of this could be the way he is NOW and it could be the way he IS, or some combination. (reddish flag?)
To me, that adds up to thinking he's not great relationship material right now and you're correct in thinking that.
Where do you want to go from there? Here's a thought, Just say "No thanks" as you have, and then ignore him. Don't defend your position. It doesn't need to be defended, it's fine. Don't try to convince him you're right. You ARE right, but he's not going to listen and what difference does it make anyway? Just think to yourself, "Well, THAT was interesting!" and drive on. Think of it as an experiment. (Might be harder than you think!)
I'm sure you have an assortment of problems with relationships. Both avoiding bad ones and not avoiding good ones. A lot of us have similar issues. This is NOT because there's anything wrong with YOU! This is just part of the process of getting better and recovering from the stuff you've had to deal with in the past. Physical therapy for the brain. Nothing more than that.