#1 Do you think the drive-side chain stay would clear a) a 175 mm crank (installed on a SRAM Dub Wide crankset) and b) a 56t chain ring? This will be paired with 12-speed 10-52t SRAM Eagle cassette / SRAM MTB rear derailleur. Yes, I'm looking for speed AND range

The crank length and chainring are not of any issue. However, the rear derailleur to run a 52T will be a long cage will be very close to the ground when engaging the larger sprockets. I am using a medium cage Sensah Empire which is pretty safe for a 11-32T.
#2: Do you think this steerer tube can be used with the stock Kabon fork?
https://vi.aliexpress.com/item/1005005485955879.htmlThis steerer will fit but comes with M23 lock nut which does not fit the fork. Furthermore, the stock M20/P1.0 lock nut has a 32mm top lip which does not fit the carbon steerer mount column which has an internal diameter of 29mm (if I remembered correctly).
#3: What nut bolt size does it use? M23?
It uses a M20 Pitch 1.0 nut bolt which is a pain to find for an alternative.