Do anyone know how the damage modifier is applied in the game? For example some weapons can have an enchantment on them that give 30 points of stamina damage. Is this damage always 30 points or is it also dependent on other factors and skills? If you have for example 100% perk in skills for weapons are it actually giving 60 points of stamina damage or are these "extra damage" points always as is?

I believe enchantments aren't affected by weapon skill. However, some enchantments I believe can be affected by a magic skill.

For example, I believe a fire enchantment can be affected by some destruction perks. I may be wrong though.