Help with stray cat(s)

Over the last year I have somehow acquired 5 cats (up from zero - my cat had recently died) My neighbor had several outdoor/barn cats that he stopped taking care of, and they slowly started migrating to me. I noticed they were covered in fleas and ear mites and not being fed regularly. The neighbor was also not taking care of himself, so I didn’t see the situation getting better and took over the care of the cats. I got them into the vet and they had a host of issues - I don’t even want to say how much I spend monthly on medicines and prescription food. Anyway, that’s where 3 come in… I slowly moved them inside and they are happy to be clean, bug free house cats. Number 4: I had a very scared intact stray Siamese/Seal Point in my backyard for over a year that I fed. I put up a house for him and put up with his hissing and swatting, continuing to feed him and give him fresh water, trying to gain his trust. I had someone come out and try to help me check him for a chip and TNR him, but it was impossible. Then in January, he got injured. He was agreeable to being helped and I took him to the vet to get cleaned up, neutered, shots, etc. They then told me that he was FIV+ and shouldn’t be living outside. I have learned a lot about FIV+ cats and understand that it is not easily spread, as long as there aren’t any deep bite wounds or bad cat fights. I kept him in my office while he got his hormones out and healed up. I was not ready to take on a 4th cat inside, but struggled to find anyone to take him with his (bad) attitude and FIV status. So I’ve slowly tried to introduce him to the rest of the house. I’ve read all the books and watched all the videos. My indoor cats have just become very territorial and as much as the Siamese wants to be their friend so badly, they still can’t be left unsupervised. They’ve gotten into some tough scuffles. I’m getting ready to move and think this will be a lot of stress on the whole lot, myself included. The good news is, he’s soooo swee