Regarding Q5...
Been a while since I last worked on Falcons and indeed I haven't worked on a 2000 or 2000EX, but on the 20 and 50 series with GE CF700 engines, the reason for choosing DC power as the primary power source was, I think, entirely down to the fact that the engines used Starter / Generators.
During engine start the aircraft batteries were series-up to provide approx 48VDC, but the respective starter motors were 28VDC. The current drain on the batteries during start up was in the region of 900 amps and this effectively volts dropped the 48VDC available down to around 28V. As the engines spooled up the series connection dropped out and the starter motors became 28VDC Generators. So the one device became dual purpose, Starter and Generator. The changeover from Starter Motor to Generator was managed by Generator Control Units mounted in the Right hand Radio Rack.
Given the relatively physical small size of the Falcon family, i suspect voltage drop due to long feeder lengths was not considered to be a problem and AC power wasn't required for most of the aircraft's systems. Some flight instruments, the radar and the cabin strip lights were AC powered and this was derived by feeding the DC to 3 x 750VA Inverters providing 115VAC 400Hz and 26VAC 400Hz; these were normally mounted up in the nose cone. An Inverter switch on the overhead panel when set to 'ARM' would automatically switch in No3 if one of the other two failed.
Some exec versions had another independent inverter providing either 115VAC 60Hz or 240VAC 50HZ for domestic applications such as Video players and TV monitors.
I suspect the same regime possibly exists with all Falcons and for the same reasons. Besides...28 Volts much easier to play with than 115v...and no problems with phasing...
pp