Please someone tell me there is a way to stop my male cat peeing in the house!

Background...About a week and a half ago I came home and a lovely little cat followed us into the house. He sat on my lap and then plonked himself on the sofa and went to sleep! I left the door open but he stayed. When I had to go to pick up the kids I decided to take him with and go to the vet (no collar).

I took him and he wasn't microchiped so decided to keep him while we tried to find the owner. Bought him some basic stuff and brought him home for the night. We knocked on the doors of our and close streets and put up a sign...nothing.

The next day he ran away kids were devastated and we'd been talking about getting a cat anyway so we went to the pound and bought a cat. Arrived home with our new (female) cat and there was Oscar (the male cat) on the doorstep.

So I decided if no one had claimed him by the following week then I would desex, microchip and register him. He'd peed a bit in the house so I decided till we got him desexed that he had to stay outside. The week he was outside he came and went and then on Tues I got him done and he's been inside since.

I thought the peeing would stop once we was snipped, but it hasn't My house smells...i've got air fresheners everywhere. I bought some cat repellant but it doens't seem to be working. I caught him twice and sprayed the repellant infront of him (not on him) like the girl in the pet shop said but I don't know what it did, if anything.

So any other tips?

Also any tips to get the smell out??

Also, he keeps meowing at the door, is it cruel to keep him in???

TIA guys