If I have the ball and I am tackled while in my dead ball area is the ball considered to be touched down?

YES. If you carried the ball into the Dead Ball area you opponents are awarded a 5m scrum. If you received the ball from within the dead ball area you awarded a 22m Drop Out.

If my player is tackled can he still pass the ball?

NO. The tackle is considered to occur immediately and your player is wrapped up in the tackle and can not get the pass away. The only exception to this rule is the 'Flip Pass' Pressure Play card.

If I have the ball can I be tackled in my opponents turn?

NO. If you have the ball then tackling will only happen in your turn. The best your opponent can do in his turn is position his players next to yours and force the tackle when your turn starts.

Can my player Move on to a grounded player, play a Hand-off card to avoid being tackled, and then Move off the player?

YES. As this player has a Hand-Off card, he therefor runs no risk of ending the turn on top of the grounded player, so this is technically a legal move.