I think it's unnecessary. May as well stick with plain spokes, which are more straight forward to buy. If you're going to put any idea to hope, it should be HURRY UP WITH A 116mm PRO II.
Modulation? Ali C explained that. If the pads are bitey, running them so they engage one at a time will give you some modulation. Of course, other people will just set up their brake shite.
Pretty much, no one else makes a replacement for an onza hub, so you're a bit stuck for choice there. Looks like you'll have to get the onza one anyway.
If it didn't work, it was because it was blunt. You can use a hacksaw, that's the universal method for cutting metal, at least, bar metal. If you have an angle grinder, whip that out.
The number means how many times the rear wheel will go round for one rotation of the crank. 1.2 is low, 1.8 is hard, for example. Stock gears are lower because the wheel is bigger, which means to get the same motion out of a mod, a higher ratio is needed.
Whiteboards are shiny, so it would reflect the light of the projector. Admittedly, that's the point, but there'd be a big round glowing spot on there. I think they work better with a plain white flat wall. You can get projector screen things though, that pull down like a blind.