Yeah, pretty much. I used L-Pad as a generic term for the volume control. I suppose that it may be a T-Pad.

They don't stay as constant as one might hope, they vary over the range. If it's important I can run an impedance sweep of 16 ohm 806 driver with the N-500 crossover.
The low pass section will still be whatever the woofer impedance is, at least below the crossover point. The crossover point will shift, however, if a different impedance is used.

EDIT: Come to think of it, more than shifting, the crossover will peak a lot at the crossover point if the wrong impedance drivers are used. I doubt this will sound very good. :-/