From just post Cascade. Going with the idea that the showdown with Karkat happened like barely minutes before Cascade.
Doc Scratch convo happened before his showdown with Karkat. Didn't do a damn thing about his rage-boner. In fact, kinda made it worse. Rough timeline here
Until canon confirms one way or another: his typing quirk isn't stable. The calmer he is, the more consistently he'll be using his old AlTeRnAtInG cApS. Fully switching over to new? Really bad sign. More on the unstable quirk here canon confirmed he's sticking with alternating lines!
Still in the worst throes of withdrawal, and will be for a while. Doesn't want to go back on the slime even if he had any though--he's a lot clearer headed and likes that. Feels like being all spaced out was what let him be taken for such a monumental sucker in the first place.
His short term memory will always be shit, and he'll be prone to losing the thread of conversations very frequently until the withdrawal is over. His overall intelligence will seem to rise significantly but he's actually damaged from the years of slime. The slime just dulled his wits down to nothing at all so being clearheaded is a notable improvement.
Without the slime to suppress everything to almost nothing his emotions will throw him for all the loops for a while. When something makes him happy? He'll be happy. Piss him off...well. Yeah. Emotional roller coaster, in a sense.
Doesn't want to kill people, and doesn't care much about blood color. However, he has an extremely overpowering urge to kill everything that doesn't have indigo or some shade of purple blood (and most times even purple blood wouldn't be safe). He'll struggle for the rest of his life, and probably pretty unsuccessfully until he gets used to dealing with undimmed emotions. So yeah, really mentally and emotionally unstable.
Guilt/remorse-- only feels honestly strongly guilty about Nepeta (partly because I also headcanon them as fairly close friends behind the scenes) because while Equius was knowingly getting in his way (and didn't struggle when he could have), Nepeta was just avenging her moirail. She had every right to attack him, and he killed her anyway. Equius is more of a mild "Fuck, that was a stupid thing to do" feeling, and any actual guilt associated with it is solely because he hurt Nepeta with what he did. Vriska he'd gleefully manipulate Terezi into murdering again, given the chance, and the universe fuck ups he will apologize for, but the emotions he feels are more tied up in "I fucked things up and hurt Karkat and myself" than actual guilt.
Consequently, he'll acknowledge that what he did was wrong (if only because it screwed the group's future over), and that he fucked up majorly, but the only thing he'll get really emotionally worked up over is Nepeta's death.
His faith is in shambles. He is strongly doubting that the messiahs are real at all, but he desperately needs something to believe in. For now, most of that will just be on Karkat. Temporary measure, but he needs something to lean on until he can stand on his own two feet again.
Random facts
Tallest of the kids, but also one of the skinniest. Very fast and flexible with a lanky kind of strength.
Will have the scars on his face forever.
He has a very lyrical voice! And while sober, also has perfect pitch. When he's happy and calm, his tone and pitch will go up and down--kinda singsong and volume differences won't be too harsh. There and noticeable, but not as stark as yelling then whispering. It's much easier on the ears now that he's not stoned; almost musical. When he gets upset and ragey he'll still singsong a little, but the biggest differences will be in volume--shouting one minute, whispering the next.
Withdrawal symptoms are severe migraines, dizziness, nausea, loss of appetite, insomnia, increased fear and unease (including screaming/raging nightmares), tremors, severe mood-swings, fever and aches, and increased sensitivity to light, sound, and pain. Will last for several months, though with marked improvement after one or two.