20K is a lot! I'm afraid to calculate my yearly expenses... lol... But, I would encourage your off-grid idea as I've been thinking about the same for some time... It's a ridiculously huge amount for "just living" as you didn't list anything luxurious...

Living in the woods, with fresh air, and fresh vegetables from the garden sounds much more appealing than spending money and living unhealthier in the city...

I agree with your opinion about getting older we get more stuck in the "system" even if we are against it and aware of it...