Older Sony mirrorless have most of what you’re looking for. I got a Sony a6000 for 350€ and it has auto iso with cap (but not auto shutter speed with cap), pretty good custom controls although I wish for more, great size, great autofocus. It does lack great low light performance, I also struggle with that, but maybe a full frame would be better for that.

You may want to try it out for cheaper and then buy lenses, and once you’re committed to the ecosystem buy a nicer more recent Sony.

About mattresses. I hike and backpack and I can attest that sleeping on the ground (meaning earth and grass) with a tent and a pad is fantastic. But you can’t really do that in your house. I’d love to, cheaper, less noise, less hassle, but the floor is hard. Even with a big air mattress I find it extremely uncomfortable. I’d love to try a hammock, but without an expensive stand you can’t comfortably set it up in a house. Advice?