We had two stray cats, one was confirmed FIV+, the other not, they didn't really get any recurring infection, but they both started having the same neurological symptoms: they lost control of their back legs and sphincters, had trouble walking straight and cleaning themselves so we had to do it.
I don't know if this is a regular outcome of FIV, or if it's even related at all, but you might want to look for gradual problems with walking and balance. Not much you can do unfortunately, but what I can tell you is they don't get any less loving, actually, they probably get more. His last days one of the strays went from barely staying close to a human unless being fed, to purr, pets and constant headbutts.
Good luck with your little fella, glad he could find a caring home.
To be fair, they started developing symptoms much later then when we took care of them. But yeah, we had a lot of cats in the years, 90% of them were strays (or in this case, one of them was actually kicked of their house and spent some years outside) that self-tamed over time lol.