So, even after doing the research I'm a bit confused on what passive damage bonuses affect what.

Right now it's a question for me of spending my last point on 10% attack damage or 15% melee weapon damage. The only skills I have are melee skills, i.e. they state "Attack: require a melee weapon to use". Does this mean that those skills are impacted my increased melee weapon damage? or are they impacted by attack damage only? or do both of those fit into the equation? And if so, how?

In other words, does melee weapon damage increase my weapons base damage before other effects (skill additions, etc), and Attack damage increase after skill additions, or are they all added into one big lump at the end?

If both are pretty much the same for my melee skills, then the 15% melee damage is the obvious choice. But I want to make sure that I'm seeing it correctly.