Null, what you are feeling is something I struggle with everyday. I'm a bit older than you but facing some of the same concerns. I'll never have a family. I didn't want children or anything, but thought it'd be pretty nice to have a relationship with someone I had good rapport with, but that has passed. This is the time to really be worrying about it. We just get uglier from here on out.
The fighting for free speech thing isn't worth it anymore. We've lost and it's a matter of time. That's why I was sort of laughing about it when it was announced. I gave up. If they want KF down they'll find a way to take it down, and they probably will eventually. The wider culture has shifted away from caring about free speech and things are just going to get worse and worse.
I disagree that the forums are not special. Null, this is one of the last places I can post. I've been banned from most everywhere. You can't communicate with anyone anymore! But still there is KF. Null, maybe this place isn't what it used to be, but it's still something, and if KF goes there too goes most of the worthwhile edgy Internet. I'm sure it'll so down someday, but I'd prefer it to be later instead of sooner. Yeah, it's starting to be kind of like a Something Awful now, but this place actually retains SA's good parts and few of its bad parts. The main reason SA turned to shit was because Lowtax was a faggot and his moderators and friends were faggots. It's not the same here.
If the lolcow thing is over--and I don't think it is--then transform the forums into something that embraces the widening of purpose to fit its widening userbase. KF is pretty much the last big community where the spirit of the free speech web 1.0 mentality still exists. It's really okay if it changes. It's still something good.
So, to address your three main concerns:
1. How do I move into stability and towards a more fulfilled person?
Do this internet shit less, do real life things more, and go and do things you've never done before. Hopefully they give the world back to us sometime soon, with this coronavirus shit. The internet is garbage, it's barely worth saving at this point, and you don't want to spend your life with all your memories being behind a computer screen. You know those memories about internet drama don't last like your salient, real life experiences.
2. How do I refocus my efforts so my workload is more manageable?
Keep the free speech shit more in your personal domain and less in your financial/economic domain. Don't try to make your money on fringe free speech business models and shit. Chase the money first and foremost, this is your life and more than half of the people whose free speech you will defend will not defend yours.
So put back the dial on the free speech stuff, and increase your priority on making money, even if it's just in terms of your psychological attention. Increasingly rely on moderation staff. Put people into positions based on how level-headed, reasonable, consistent, and fair they are. Don't be a Lowtax and select your leaders based on them being friends of friends. That's what really fucked things up, SA was run by idiots.
If the forums are making life worse then step away from them however much you need to. You don't owe anyone anything.
3. How do I have fun again?
See my answers to 1 and 2. This life on the internet shit is something we are too old for, I've missed out on a lot of experiences sticking to my computer all day like a fucking nerd. I'd suggest develop yourself in some skill or hobby that has nothing to really do with technology or computers or the internet.