Hi Tim,
Welcome! Great pictures. You asked how many cats are too many, I say there are never too many. I have 11 right now, just had 4 kittens on Sunday/Monday. But the town I live in has an ordinance that you are only allowed to have 4 pets. But what they don't know won't hurt them. They are all vacinated (at different places) and are spayed and nutered (except for the momma and kittens and they will be as soon as they are ready)
Are all your cats indoor? Mine are, it is a good thing we have a big house.