On the tweeters let me say that I really like the Pt2 planars versus the small domes eventhough you don't have that much array gain. If you have to increase the sensitivity, then wire them for a lower impedance (a 4 ohms array would yield 3 dB more sensitivity or slightly more than 95 dB SPL).

Unless you have very small domes you are not going to realize much array gain with them when you go beyond a wavelength center to center spacing as it is.

The only way to get into the upper 90's dB SPL is to use more expensive ribbon tweeters (Founteks from Madisound or Aurum Cantus models from E-speakers). In contrast the Pt2 planars are one fourth or more less cost per device.

On the woofer crossover I think you need to be thinking about a lower than 6000 Hz cross point. The directivity of the woofers will start to fall above 3.4 kHz for your case so you will be getting less array efficiency as you go above that frequency point. With the active bi-amp'ed crossover you can address both the crossover point and any gain offset between the two lines at the same time. Just takes more amplifiers.

Jim