Tip tackles aren't legal in rugby league. Anything that goes past horizontal is penalised. There seem to be less grey area tip tackles in league than union.
If he hadn't illegally popped the ball off the floor, then Priestland would have had more time to get behind the back foot. The first offence was botha, so you're wrong
The ref made the wrong call earlier in the game with the Priestland yellow card. Geoff Parling didn't play the ball immediately when he went to the floor. The ruck formed over him and then he popped the ball up to Corbisiero. It should have been a penalty against Parling. Ironically Wales played there best rugby when down to 14, and kept up the good work when restored to their full compliment.