It doesn't match all of your wants, but you should consider living in the inner city of a large metropolitan area and working for tech companies there. In Los Angeles, a talented dev/arch with devops can make $185,000/yr with benefits. Another possibility would be turning into a migrant fruit-picker, stick your stuff in a storage facility and follow the contracts around the country, looking for the $200/hr gigs.
Do all of the above, then retire early and spend your time developing your own client list at your own pace at home, working 0 to 10 hours per week.
One thing you might consider is expanding that "Spring Boot" to "Full Stack". It will give you some options when they decide they don't want a fussy gray on the team and cut you loose.
When I was 30, people just looked at me and assumed I was a competent software engineer because I looked exactly like a very senior software engineer, and I presented myself in that way. But I was very junior, having made a recent career change. Yet they paid me like a prince, and I rose so rapidly through the ranks that I became an executive.
Now I'm 50, and my company folded and I went to the curb, and am looking for a new job. Now I don't look like that bright young engineer. I look like an old has-been who is stuck in a rut and stuck in my ways. Except I'm not. I'm highly experienced, an innovator, get along great with many kinds of people and can contribute at all levels of an org, from production support to development to architecture to the boardroom.
But the first question I get asked on interviews is "Are you technical?"
My over-40 career advice for you is to remember what they do to engineers that are over 40.
The yelling is unprofessional and doesn't represent us well as a country. However, the import of undeclared fruits and vegetables can do damage to our ecosystem if they are of a type that represents a danger, or carries certain insects.
Also, and I know humor is generally frowned on here, but yelling in the presence of durian is understandable at a certain level, if you've ever tasted or smelled it.
Do all of the above, then retire early and spend your time developing your own client list at your own pace at home, working 0 to 10 hours per week.