I empathise with you. The ones that force us to act in a way that is against our dreams of giving them the best life possible make us weep with frustration. It seems to me that your choices are:

Mood-altering drugs. But it can take months for these to kick in, they don't always work, and even when they do it's not a total fix. Taranis has been on Prozac for about six months. She rarely pees on things any more but she still can't stand having other cats near her. She's been bounced into four homes so far and is unadoptable.

Cat run. I don't think you have room for one more and she'd cause fights in there also. I hate the fact that LOS is in one bedroom with twice daily access to the garden and beyond. I know she could get hurt out there, die out there, but she needs exercise and if with the others she does nothing but hiss, growl and fight, causing great disruptions. Tom is her companion and he'd douse my entire downstairs if I let him out of their room. Since Thumper is already doing a good job on this, I don't want the two of them to start a competition! They may have shorter lives, but I can't do more for them.

Park. It's the only solution that will truly free you and all your other cats from the terrible strain you are all under. You may have to sacrifice this one to the rigors of park living in order to give many others the life they need.

I'm with you and Jenn on trying to live with the ever-present smell of cat pee. Fortunately, that's only in the downstairs rooms for me now but it's still back-breaking and dis-heartening.