So I finished the game and i decided to redo it but this time with cheats to see the difference of difficulty and i was setting my level to 90 to get xp but I accidentally set it to 900 and now i randomly will run into people or creatures that are level 900 and take forever to kill. is there a way to reduce it with mods or anything? because the game doesn't allow me to setback my level. Any help would be appreciated, thanks!

Unfortunately, no. The console command only increases level. You'll have to reload a save where you weren't level 900.

You should be saving often.