> 4) I like variable width fonts, and variable width fonts don't seem to work with various bits of org mode (for example tables)

Same. I use mixed-pitch[1], a package on MELPA[2]

  M-x package-install mixed-pitch

will take care of Org tables and more. Doesn't attack the problem minimally, but comes with sensible choices; it's been basically a drop-in-and-forget activation snippet.

[1]: https://gitlab.com/jabranham/mixed-pitch

[2]: https://melpa.org/#/mixed-pitch