Is the damage that Musketeer power's do (I.E- Grapeshot, Hurricane Round, Rain of Cannonballs, etc.) based on Weapon Power, or Spell Power? Or is it a weird combination of the two? Thanks in advance for your answers!

Spell power my good man. That is why some muskets bring Ol' Scratchy along, as he can make your bombs deal around 1k damage.

It depends on the power. Powers such as Grape Shot and Hurricane round use weapon power while bombs and Power Monkey Palisade use spell power. You can tell if there's two swords (weapon power) or a mojo potion (spell power) on the card itself.

Fun fact if i'm correct: When you hit someone and there's red text where the damage number should be, that means your hit was based on physical damage, while yellow text (I know this is orange bare with me) means that your hit was based on magical damage.

I just tested it and despite the cards saying that bombs on the ground do physical damage, it still has yellow text so i'm not sure if this is a error or something, but it does similar damage to the first hits so i'm pretty sure that bombs left on the floor are still magical damage.