Up until today things seemed to be looking up, the cats have been fighting way less, and when they do fight it's been milder hissy fits and not trying to kill each other. Kiri has been keeping to herself in one area of my living room but she has seemed happy enough and Killer has been leaving her alone for the most part. Killer stopped vomiting and acting sick after only a day or two of antibiotics and tbh I don't think the antibiotics really did anything.
However, this evening Kiri inexplicably urinated on my couch, right beside me, as if she wanted me to notice it. I know that this can happen if a cat is stressed or it's too afraid to go to the litter box, but the box is literally right beside the couch, and she didn't seem overly stressed at the time. Almost immediately afterwards, the cats got in their worst fight in a long while.
I honestly don't expect anyone to have any clear answers on what to do since I believe I've done close to everything already, but at this point I'm just hoping for reassurance that all this drama will someday end. After almost two and a half months and hundreds of dollars, I'm wondering if it might soon be time to look for a new home for one of them. I don't want them to be in a state of constant fear in their own home, but I don't know what else I can do. Keeping them separated in my one bedroom apartment just can't be the long-term solution.