1. Damage *never* “wraps” after a kill. If you deal 35 damage to a player at 1 HP, they still respawn at 20.
2. When you redirect an attack, you completely gain control of it as though it were “yours.” So if the card said “for each player YOU killed this way” you would NOT gain the +3 POWER. However, since this specific card stipulates that the person who played the original card (not the attack) gains +3 Power for each kill made with the “card” yes you will get the +3 POWER from your opponent redirecting the attack and killing you.