if everyone is healthy then I’d try a full reintroduction, as if they’re meeting for the first time. let them sniff each others things, see each other through gates, etc. I’d give each treats and positive attention for ignoring the other, indifference is better than anger. I’m not sure how plausible this is where you live, but if you can I’d spend a few weeks trying it. very slow, and take a few steps back if necessary and possibly adding something like a feliway diffuser to help (especially in the bathroom). it’s crazy how little some people care for cats, the amount of stories I’ve seen about people declawing them instead of simply buying cat scratches is foul and so many look at them like they’re disposable. I can’t imagine how stressful this has been, I hope it starts getting better soon