Some of your questions are best answered by someone from the DAC group.
Administrators need to move this question to HS-DAC.
1) The DAC software suite uses a PIC (via an external host) for SPI control. The HDL designs we have do NOT, the SPI control is from the FMC. However, you should still be able to port the design over to ADS7.
2) Same as 1 above (DAQ2/HDL designs/Linux images are all parts of the same system).
3) No-OS & Linux Images -- http://wiki.analog.com/resources/eval/user-guides/ad-fmcdaq2-ebz
4) Yes, assuming the AD9144 FMC boards support it- it will be same for any other carrier with 2 HPC. If you are looking for any existing reference designs, HS-DAC team may be able to help you.
5) Yes (if you can do it yourself - I don't know of any plans about this in other teams)
6) No, DAQ2 boards the clock chips runs independently with their own crystals, there is no mechanism to synchronize the AD9523. charlyelkhoury might be able to suggest some board modifications if you want to synchronize them from a single external source.