The one thing I don't see in your diagnosis is voltage to the gas valve.
If the ignitor is glowing, the next step is for the board to send 24 volts to the gas valve. You should hear it click when it opens. If you get 24 volts at the gas valve and it does not open, you have a bad gas valve. If you do not get 24 volts at the gas valve, you have a bad control board.