First, happy to be testing the game out, second a big fan.
I don't agree with the Dim light = Disadvantage in Melee when some one has darkvision. Please reconsider following the SRD on this one.
Per the response given in the forum, You can just change the lighting when that character is selected to represent the character's vision capability.
Also I casted light on my character's amulet, and it had no impact, however it does work on a weapon.
The only other way around this was using a torch.
Adv and Disadv not cancelling out:
Advantage is not cancelling out disadvantage: Sorak was prone, and in melee (in darkness with darkvision) still had disadvantage.