Went over several name options and have decided on Caelus; "Cael" for short, sort of "kel" in pronunciation
For the first half of the day I was alternating an hour with him in free roam (in my room) and an hour with him locked in the bathroom (so Oz could have some time without him around). By evening, Oz was mostly sleeping anyway so I let him hang out uninterrupted while ash spent the evening with us in my room. He is very polite and mostly backs off when Oz hisses at him, but he is a kitten and really wants to stalk and chase her. Things got a little stressful a bit ago, so he's back in the bathroom for his dinner, will probably come out again one more time before bed. I can tell he's starting to get a little tired both of this system and of not being able to explore the rest of the house, so hopefully it won't take too long before things change.
We are hitting points of correction and having to teach him 'no', 'get down', and 'don't do it', which he is of course not thrilled about. He otherwise continues to be ridiculously affectionate -- we think he may have been weaned before he was ready for it, which also means he might be a little younger than reported (the previous owner was guessing), but he's certainly big enough to be twelve weeks. He doesn't have the anxiety I'd expect from a cat that was separated from its mom or littermates too young, but you never really know how that'll affect them. He's definitely very well socialised, and [touch wood] I expect him to get along with all the other animals in the house
Oh, we also gave him a flea bath (more as a preventative measure than anything), which he took better than most cats would but still predictably not great. He is a drowned rat when wet.
I really hope things work out. I'm very nervous about Oz. But I'll keep things moving as slowly and smoothly as I can