Jesus. Yeah, this entire thing hits home. I think a lot of mid- to late-career software folks are in this position of hating the work, feeling super guilty for hating the work, and not seeing a way out that won't risk their family's financial security.
My best job ever was a Summer job helping manage a campground. Outdoors, some social interaction, enough down time to read a few pages of a novel or do some pushups here and there, a bit of moving heavy things around, nothing whatsoever to think about when you leave for the day. If something like that paid 75% as much comp + bennies as my WFH software job and had similar future job prospects, I'd quit effective today and go do that. And probably cancel my home Internet service, sell my computers, and downgrade to a dumbphone. It's all just so incredibly low-value, once the shininess wears off.
I have it great; I make a 6-fig salary, I work remote full time, and never more than 40 hours. I feel guilty for complaining, but the work is just damn boring. I would rather be a janitor than code anymore. Some days I sit and just stare at my screen for an hour depressed as hell wondering how I'm going to get out of this and still provide for my family. We have chronic medical issues, so the insurance alone makes it hard to escape. The great recession also left me with severe anxiety about being broke and unemployed.
I recently rebuilt a manual transmission with minimal prior experience working on cars and it made me feel so damn good afterwards, so I really respect your decision to work on cars. I agree, it feels great to do manual labor! I spend my free time doing manual work around the house like yard work or building things like a green-house. I'm learning a lot and having a great time, but when I sit down at the desk it makes me even more depressed about coding.
I hope it all works out for you.