Uncle David, I feel for you. That's so sad. Sometimes animals just don't fit in with certain households. It's better to give them a shot at another home. Charlie might need to be an only cat. Sometimes other animals in the house get them acting up like that.
The older cat I have now (He's 11 and neutered) used his litter box like a normal indoor cat until a year or two ago. Then suddenly he started going everywhere! I took him to the vet to see if there was a physical problem (there wasn't), I tried different litter boxes, I tried using different litter, and I did anything else I could think of. None of it worked. Thankfully, I had the option of making him into an outdoor cat. He'd never been outside a day in his life, so I briefly considered putting him down because I didn't want him to live out his old age terrified and hiding under bushes. However, he's adjusted quite well and is still allowed in for naps and such. He's a happy cat, but I still feel guilty sometimes that I couldn't figure out how to let him to continue to live inside. I'm am glad I could put him outside, though. Not many people live in an area where they have that option.