Please help me make the best decision for this poor cat.?

The cat I trapped today, Feral, 1-3 years old is infected with Notoedric Mange, mites living under the skin. He also has FIV positive. I was hoping to neuter him, find him a home, but now, not sure what to do. I have two pets, living in an apartment, I have the cat in the cage in my bathroom. What should I do, would it be wise to release him, but he still needs two ongoing treatments for the mage, revolution (according to the doctor, but his is the extreme case, usually revolution I thought is for mild mange cases) Anyhow, choices are to ask shelter if they can keep him for a month, until he gets his treatment, and then release him to the same place. Second, to put him to sleep, not release him due to his FIV positive, etc. I don’t know what to do, I can ‘t keep him for the risk it has.

Do not release him till his treatment is done, just keep him seperate – this is CURABLE except the FeLV – if you hanD this cat to a shelter, the only words they hear is FeLV and they”ll put him to sleep.