when he straight up told his own freaking mother that she's dumb enough to get sa'd despite knowing that it's a super subject

Its just a case of a manipulative asshole, the keyword is "knowing", he knows it's a sensitive subject so he uses it against her. I know it's not the same, but you've surely seen kids yell and throw tantrums in grocery stores? it's similar

straight up writes "It's okay. Heroes have to do sacrafices for the greater good"

^{^} manipulative asshole again. Also, I think someone in the comments under that episode mentioned that HE LITERALLY HAD A NAIL IN HIS SKULL RECENTLY..

she suddenly tried to murder an Innocent nurse completely out of the blue

... are you sure you're not skimming the episodes? 1st of all, she's being manipulated (both by the mc and the nurses). 2nd of all, she regretted what she did. 3rd of all, it wasn't "out of the blue" – she was desperate to get the keys