You should fix those things. Or don’t use flakes at that point, you’re not really using flakes anyway since you’re setting nixos-config which is ignoring the flake.nix.
Unnecessary with flakes as the flake is copied to the store before eval.
You don’t need NUR with flakes, NUR is a pre-flakes way to expose some common projects.
Most of said projects are also flakes that you can use directly if needed.
No? You just have to use a valid path. The error tells you as much.