Now, I'm in a (functional/people) management job that requires more focus, but pays three times as much, in a different and more expensive country, so it probably works out to around 2-2.5x as much. With the recent addition of a competent senior manager under me, I'm able to slack off a bit - a bit, not a lot - and play with my hobbies between or during particularly brain-dead calls.
tl;dr management, and fill the ranks under you with good people. I know you said you didn't want to manage people, but unless you're VERY good with creating novel AI, it's probably the fastest route to your goal. I recently did a farm management course with a guy who hammered home the idea that you need to focus on your desire/objective/goal, really understand what you consider important, and not set obstacles for yourself at the outset that would prevent you from getting there. His frequent refrain is that he could meet his goals "in prison" as long as he was willing to be flexible about how he achieved them. Give it a think. If you get to pick the people, having a weekly sync is a lot less effort than trying to write software part-time.
Another important area for you to focus on is cost management: if you can go, or make a 2-to-3-year plan to go, somewhere that the money you have now will buy a house outright, you can potentially live off a hell of a lot less. Reduce your monthly living expenses to exclude a mortgage or rent and include only food+utilities+tax+insurance+hobbies and you may find that you can get by with part-time employment, seasonal work, or time-limited contract work of your choosing. There are many flavors of this: go work in the sandbox for Raytheon, do a month on and a month off on a rig, get a job on a ship, go do a stint at a mining camp when you need cash, etc. All of those places need people with tech skills, and they're probably full of people who are in it for the money and because they love the vast expanses of free time between deployments.
N.B. I'm American, and have been in Europe for 18 years-- so yes, if you're in the USA, a move to somewhere with a more healthy work-life culture could potentially be realistic for you to consider. The Netherlands is not a bad place if slacking in English while maintaining a high standard of living is your goal.