I don't use any specific palette. I either stick with a palette for a project or just add colors as I go and try to not add too much.
This particular tileset uses 4 colors so it should be easy to map to anything you like. Pico8 version might e.g. look like so:
Why not? This is one of the strengths of pixel art after all :) You can even change it mid game with a simple shader (and people do so since forever)
And yes, most people should be able to add something to it and it would still look coherent (which is imo much more important than looking good).
As for LÖVE: well, there is a lot of stuff out there to learn from but unfortunately I'm not aware of any comprehensive from 0 to a finished game course. This is a great idea for a side project :D (no promises).