Hello. Which mod framework are you using, Oxide or Carbon?
Are you sure this issue is caused by RealPVE? Have you tried reproducing the issue with RealPVE unloaded?
For reference, bulls, cows and calves have 450 HP by default, so you should check which of your modifications is changing their health to 250 HP. You should pay more attention to the modifications you're making.
Regarding damage to cows, do these cows have an OwnerID, or is it set to 0? Also, please check if you have /adminpve loot self enabled, as it disables restrictions.