I apologize for my ignorance, but I am still not understanding how to set the fuel pressure on the nitrous side. Do I remove the small AN line going into the plate, somehow hold the jet in place, manually actuate the solenoid, and then set the regulator?

Yes. The way I set mine is. I remove the small braided line after the NOS fuel sol'. Then I made a special line just for flowing the fuel. The line screws onto the Fuel sol' & the other side I made a fitting to hold my jet. Then turn on your pump & set fuel pressure as it flows thru the NOS jet. Or if you want you can just remove your NOS plate, an leave your jet in it and flow thru the plate.