Man this whole "must remain friends" is ridiculous. When he brings this up or pushes it, pls remember that "no" is a complete sentence. If he pushes further, say you're not interested [in remaining friends]. Does he think yall are friends right now? As good as I know it can feel to launch into the whys, I think itd be better to just not engage. If he hasnt figured out why you dont want to be friends right now, hes not going to - plus hes just using that as a way to scuttle off guilt free. Idk if you've ever read about dont JADE (justify, argue, defend or explain).
What part of moving out scares him? Admitting to himself that hes being a $hitty person? (My guess)
He seems so irrational and out of touch with reality. I think if you go as dark as you can thatd be best for you - you dont have to engage in this crazy making crap with him, and he then no longer has the benefit of releasing those crazy thoughts to you. Hopefully he then implodes or tells someone not directly involved and they smack some sense into him. But the real benefit is you having time to yourself to think about what you want and your plans instead of absorbing these insane ideas of his.