First of all let me say I absolutely LOVE what you done in this game, its an amazing implementation of the 5e ruleset in a cRPG, way better than what Larian has done so far in BG3.
My absolute only real complaint: I believe the rules regarding light hypersensitivty are wrongfully implemented. Creatures with this feature should not have disadvantage because simple things like a light spell, or a torch, only direct sunlight shoud cause it. Because of this, some fights that should be hard become trivial, and thats a shame. Advantage/Disadvantage is a massive deal in 5e, it would be nice if you could take your time to take a look into it.
Maybe the confusion exists because previous versions of DnD had this kind of sensitivity, but AFAIK in 5e theres only sunlight hypersensitivity. You can refer to the Vampire Monster for example, wich states: Sunlight Hypersensitivity. The vampire takes 20 radiant damage when it starts its turn in sunlight. While in sunlight, it has disadvantage on Attack Rolls and Ability Checks.
Cant wait for the full game! Wish you all the best!