Played around with the mod (and the source a bit). It's pretty neat stuff, although it does get crazy, especially when playing with mods like calamity that have very tough monsters, or when using something like enemy stat config for when someone wants to challenge themselves and play against tougher monsters.
suggestions (warning, incoming tl;dr):
1) like others have said, that % damage per level should be nerfed a little. (halve it to 2.5%/lvl)
2a) the reduction stuff (for damage, mana) should be linear, and be capped at level 100. (e.g. +0.75% reduction/level until level 100 or something)
2b) same for added wing time. cap it at level 100 or something.
3) there should be an upper level cap of 1000. good enough for people who want to cheat or whatever.
4a) make the experience growth "polynomial" at first, and then add a bit of exponential growth starting after level 100.
-i recommend (growth*level)^(some constant power a little bit over 1) for levels 1 ~ 100. starting at level 101, the experience requirement should "jump" by 25% every 25 levels.
so it'd be 1.25*(that "polynomial" thing) at 101, 1.25^2*(that "polynomial" thing) at 126, 1.25^3*(that "polynomial" thing) at 151, etc etc.
4b) for the experience gained calcs, instead of divving by 100, take the square root or some other fractional power to complement #4a. multiply it by a constant if it seems too slow or whatever.
5) perhaps, as a bit of an "anti-cheat" device, make it so that monsters start getting tougher after level 100. much like how the experience requirements would do 25% jumps, the monsters' stats (damage, defense, health, whatever) should jump by 20% every 25 levels, with the first jump happening when player reaches level 101.