1. It's not that CPU intensive.
2. Best to refer to the changelog --
https://github.com/EQEmu/Server/blob.../changelog.txt
3. Client support, lua implementation, etc. again refer to changelog
4. Pathing has gotten better from even two years ago, with better bestz computation and new(er) path/maps released
5. Difficult to say because I havent played live in a very long time, you should just grab the repack (or compile your own) and find out tbh.
6. P99 seems to be experiencing all time highs, though server population is on home page.