Help!!! So I just got to the part of te Main Quest where you trap Odahving, but I can't hurt him at all!!! Not with my sword, not with the few magic spells I have, and not with shouts! I'm stuck!!! I'm also unable to complete repairing the white phial quest and blood's honor. This happen to anyone else?

This isn't a glitch. You aren't supposed to really hurt him. You have to lure him underneath the trap that's inside the "garage" part of Dragonsreach. He'll follow you back there if you get close enough to him.

I thought the various quest related NPCs made it pretty clear that you're trying to Capture and interrogate him, not kill him.

I think OP means that he cannot damage Odahviing enough for it to land...
Have you tried exiting and reentering the area, or load a save before entering...? Did you use Dragonrend..? (I actually think you need to use it in this quest)