I just killed my ex-husband and before he died, he moved in with me. Now his ghost is here and I don't want him in my house anymore. Well, I do, but I don't want to control him. I have enough sims to control as it is. What can I do?

Just ignore him. Sims can generally take care of themselves so you shouldn't need to pay any attention to him.

I think there might be mods that can make sims in your household act like NPCs whereby you really don't control them, but I can't remember what they are. You could try checking the WCIF forum for those

By default, a ghost is not a controllable sim. To make him controllable, you'd have to do the "Oh My Ghost" opportunity from the science lab.

To get rid of the ghost, you can take the headstone to graveyard... I haven't done this for a long time so I don't recall the exact procedure, but I think it's an option you choose from the "Manage Dead" option on the Mausoleum.

Yeah I killed one of the Sims in my testing hood when I accidentally made her a vampire, thinking that killing her would cure her. But when she returned from the science lab she was a controllable vampire ghost. Not happy me, but anyway, you have to go get his remains from the church yard via the manage dead from the mausoleum there. Then in my game a day later he got an oportunity to turn in her urn via the ghost thingie. That made her controllable.

I don't know if you can click the science lab before getting the phone call. This was the first ghost experience for me.

When TS3 first came out, I didn't know sims could die (I did not play TS1 or 2) until my insane sim with no handiness skill whatsoever decided to tinker with the stereo. After she was electrocuted the first time, she decided to give it another go, so I let her. When this killed her, I didn't know what to do with the remains, so I left them on the dining room table. Every other night she would show up, and was in the portrait panel as a controllable sim until she went back to the urn in the morning. I finally figured out that I should take the remains to the cemetery, then another sim in the house got the science opportunity, brought her back as a playable ghost then fed her ambrosia to bring her back to life, and she's still part of the household today.

I have built some catacombs on the family's home lot, and the ghosts I get now don't show up as controllable, so I just assumed this was fixed in a patch.