Bridged amp question

You cannot use a 12dB/octave passive crossover without a load on all outputs. For the unused low-frequencies, you may be able to switch to 6dB to make them safe to use only the tweeter outputs.

For the crossovers running the mids, you would either have to disable the tweeter sections or connect a load across the tweeter outputs. A 20 ohm resistor may be enough.