I understand and accept what you say about the high-paying all-in job option. It's not for everybody and can also be damaging.
If you want part-time dev jobs, of course they're out there's lots of competition and not necessarily a lot of job safety. The lowest end are gig economy jobs (like Upwork and Fiverr) but again, buyers there are sometimes also looking for an easy, reliable, part-time go-to guy for regular jobs that maybe have a unique skill set. You can always give it a try. Chances are that you will not make enough money doing this (most likely) to live comfortably in a highly developed country (I don't know how to express this in the "political correct" way du jour but you know what I mean). However, the advantages are guaranteed 100% remote and no long-term commitment, so if you find something better, you can always take it.
Wishing you all the best. And seriously, do report back some time how it works out for you. I'm sure many have the same dream and wonder "what if..."
These definitely exist, at least in some companies. One of my former employers had several developers who worked 3 days (i.e. 22.5 hours) per week.
I'm passionate about playing a competitive sport. I could spend my days practicing / working out / thinking about tactics. Unfortunately I am not a world class athlete so money is not an option there :). I'd just be happy having enough time to go as high as I can on the local tournament scene.