If I have 10 potions of say 10 points of poison, can I apply all 10 to my bow for 100 points of poison damage?

Nope. It will say "This weapon is already poisoned" or some such after the first one.

Not on the same shot. I don't know if the same potion will stack if you hit with it multiple times, however.

Nope, since you can only have one poison on a weapon at a time. I think self buff potions don't stack either but I'm not 100% sure on that one, never really tried it.