Unless I'm missing something, this wouldn't work because the Orwin gambit gives initiative back to the opponent by sending them back to the center board when it's already full. They would have the chance to employ the strategy back against you before you could pull this off.
The Orwin Gambit actually doesn't go quite so far as to force the win, however if you forget about filling that last center and instead go for a corner, then you can continue to force them back to the same corner over and over. So the Gambit is fallible, but if you back it up one step, it can continue the force to the inevitable win.
No. You lost the initiative (the ability to force their next move) when you sent them to an open board.
I don't believe you will ever send them to an open board. O makes all its 8 initial moves in the center, and the 9th move for X will be in the last empty board. I think that it depends on what their last move in the center board is. If they send you to a corner, I believe you can force the win. If they send you to the SW corner, you make the first move in that square to the SW corner. This forces them to reply in the same SW corner. Wherever they go, you make your move in the next square in the SW corner, bringing them back to that corner again.
Nope. You can only hold the initiative through 9 moves. After X9 to board B, O9 to center. X10 can pick any board C with subposition B, but O10 can force a return to board C. X10 has occupied the forcing position = lost initiative.