I thought the minimum operating pressure on the boiler side of the NCB series is 12 psi, and that it is regulated by an internal auto-fill / pressure reducing valve(?).
On page 8 of
the manual (p9 in PDF pagination) it indicates the heating system side must be between 12-30 psi. So no WAY should the heating system's pressure be set to 35 psi or higher.
If the boiler is more than 20 feet in elevation below the highest radiator it's advisable to bump the pressure up a bit- 12psi won't work well- it's likely to collect air at the top of the system. The rule of thumb is 3 psi + elevation in feet x 0.433. There are no good reasons to run it higher pressure than that. Most (but not all) 2 story houses with a boiler room in the basement below the first floor will need to be a bit higher than 12 psi. Setting the expansion tank to the system pressure +1 psi is usually a good place to start.
You probably introduced some air into the system when swapping tanks. The air scoop & vent above the tank will eventually take care of it as long as you're getting adequate flow. It would purge the air somewhat more quickly if the air scoop wasn't so close to the 90 degree turns, which introduce turbulence, somewhat disrupting the laminar flow thorough the air scoop that lets that type scoop work. I usually shoot for a least a foot of straight pipe on the incoming side of the air scoop, but 6" will still work.