I'll throw in my explanation about the blood. I think that the reason Martinez failed, even though he gave all of his blood, is tied to the part about it needing OUR blood. My head canon is that it always needed more than one MOL to contribute to the blood. I mean they never say that, but it fits.

Yes, Sam should have been unconscious after all that blood loss, but apparently Sam just laughs at losing blood. Dean wasn't rushing him to the ER after the ghouls drained him in Jump the Shark, so Sam just seems to not need as much blood as us mere mortals.