So we've ended up with a second cat, acquired from paradoox and L. They had gotten Kimi (the cat) from the shelter a number of weeks ago (maybe 6 now?) because they wanted a friend for their existing cat, Arthur. That did not work out well. The shelter had said that she'd lived with cats before, so we thought maybe the problem was Arthur, a big, young, excited, Tom. So maybe this would work better with our big, old, super-chill Tom. Day 1 of Kimi and Monster was better than Kimi and Arthur ever was. After a week there is a lot more progress, but there is still growlilng going on (all on Kimi's side... I am *so* proud of Monster, I can't even tell you. My kitty is awesome. He's done everything right, which is amazing 'cause she's sending some real mixed signals here about wanting to play or not).
Kimi has started warming up to Gumby and I, and when she's not freaked out, or being a crazy bitch in Monster's general direction, she's very sweet. So we're keeping her and crossing out finger that in 3 months her and Monster can both be up on the bed at the same time (it's only been a week). Even if that doesn't happen, if she stops growling and freaking out, and they just tolerate each other, I'd be pretty happy. Plus she actually fits inside the tunnel on the kitty furniture, and after we put some katnip in there she decided it was her spot. It's so cute having a normal cat-sized cat around :)