This is all your interpretation, it is by no means facts, and you're taking everything at face value far too much
"Screaming in terror" Or you know, scream in pain? pain he hasn't felt in a long time it seems and pain he definitely didn't expect to feel from the scabbards of al people. People here tend to stick with some interpretation of the scenes and run with them as if they were true and in this case a lot of people just ran with the "Kaido has Oden PTSD" explanation, but nothing really proves he was scared or traumatized by the scabbbard's attack. He was talking with them and smiling in the basement just fine after the attack.
"Junkie Death Seeker" This is what we're missing here and why a flashback could bring everything together. Kaido wanting to die, wanting to be the PK and wanting to start a great war don't have to be conflicting motivations. The man seems to idolize people who died great and glorious deaths that made them be remembered forever (Oden, Roger, WB), but that doesn't mean he just wants to die because he's depressed or something. There is some fucked up implications here that Kaido believes the only way to really be acomplished is to die in some grandiose and memorable way, which could explain why he even jumped from a sky island, but since we're still missing info on his character we don't know why he believes that.
Of course he'd want Big Mom out, he wants to start a war with the whole world, and a legit full scale war between him and BM would just mean them near killing each other's crews, destorying his territory and being left as easy pickings for the WG. He would have no way of knowing BM was there because she wanted to kill Luffy and talk with him, of course he'd assume the worst if a yonko just came to his territory, it doesn't have to conflict with his war motivations.
On top of all of that, he's an irrational, impulsive drunk with a cynical side that believes the world just doesn't have great powerful people anymore, and now almost the entire new generation are there essentialy proving to him wrong, which is why he seems to be enjoying himself up in the roof.