Stop working unpaid overtime. If that gets you fired, so be it, but it's better than working yourself to death.
Your family would rather be poor than not be able to spend time with you
Assuming you're a decent developer you can get another job easily. If you seriously can't afford to not work 18 hours a day for a few weeks, then consider bankruptcy.
I don't contest what you say, but getting out of these life situations isn't as easy as you put it either. There's more to it than meets the eye, it's a little more involved than "people should get off their seats and make life changes" and so, the best thing would be to show some human empathy to these people.
Whoa.
She wants you, not "nice things". Neglecting her in order to make money to buy her things is a Very Bad Idea, because you've made yourself fungible
Plus, she does have expensive taste...
We live in an economy where if you're not putting in those extra unpaid hours you're not considered an asset to your employer and you will be disposed of. An economy where 17 old kids can not only flip burgers, they can code and code for a hell of a lot cheaper/are more willing to sleep at work to meet a deadline.
Burning out is when you go to work, come home to freelance, go to work 7 days of the week with inconsistent hours, not getting to spend time with your family, not getting to go to the farmers markets or watch movies with your wife. It's going to bed at 2am working and waking at 6am to go to work, it's feeling like you're constantly working, constantly checking emails all for the same salary.
If your work is comprised of open source, you at least have a way out. Me? I have no way out. I work on my personal projects in between freelancing and my actual job hoping that maybe, just maybe, all of this stress, finishing work at 10pm, having to come in for weekends without being paid extra and work will mean something one day. Hoping that all of this effort will mean that one day I too, can hire multiple people to do the work currently I as one person am doing.
You don't sound burnt out, you sound bitter that nobody is using your work, that's entitlement, not feeling like you're so deep in work you have no way out which is being burnt out. I am sorry to sound so aggressive and angry, but I am burning out and there's nothing I can do about it.