Is there a specific weight or do I need a vet evaluation or what?

---

Full explanation

I feed a few local stray cats and neighbors outdoor cats and a black one has been coming around. I noticed a few days ago that not only is he just skin and bones, but had a bad bite wound near his tail. So I brought him in.
I already have a male cat (fixed) named Paxton.

The stray (ive named Noir like film noir cause he’s black) slept the entire first two days I had him. Very lethargic. Honestly thought he might pass. I treated his wound. It was gushing blood then white pus. But now scabed over . I used spray bactin.

I De-wormed him. And I’m trying to fatten him up with kitten food mixed in with high quality adult cat food.

Seems to be recovering but it’s only been about 5 days and it’s going to be a while until he’s got a little weight put on him. Maybe months ?!

But hes up and moving around a bit these last two days.

It’s been stressful having him. My long term cat doesn’t really like him. Expected and reasonable.

But Noir keeps approaching him. When he needs to chill.

Also someone peed on the kitchen floor. I don’t know who, but it wasn’t me.

At least it was on lenoleum.

I’ve got two litter boxes out but they both are using both now.

I suspect the testicles are part of the issues of posturing and urinating.

Also yesterday a female neighbor’s cat visited me. She comes over sometimes.

And even though she’s fixed, Nior pestered her the entire time she was here.

I don’t really want another cat. Noir has a good personality, actually a great personality, but it’s the additional responsibility, cleaning, care, etc. So I’m going to just try to get him healthy. Fixed. Vaccinated. And find him a forever home.

But who knows how long that will take.

But I gotta get him fixed asap. Before he starts spraying all over and stressing my Paxton out.