A642:
A grapple check is a combat maneuver. It DOES count as an attack roll but it is not a "melee attack."
A643:
That is a tough one. I could not find exact RAW for that scenario. My analysis is it goes ethereal at the end. Nothing says the power is disrupted on going unconcious. It does not follow the rules of spells as it is not a spell like ability.
My instinct would be to rule it as it dropping back into where it started, but RAW I see nothing that stops it from shifting.