It's fine with 2 wg, do what you gotta do, no judgment here. The one with the lower boost spring will do the boost control and the other one will open if you reach it's spring pressure. The way you set the preload is good enough, you might want to check that it all worked out the way you thought it did. For whatever reason the flap might be open a bit and causing it to be lazy. You might have the wrong spring in the external gate, something to consider. The boost reference wont affect how long it takes to come on boost, you want short lines to the solenoid for more responsive control. This is purely how quick the controller can change the boost, nothing to do with how quick the turbo comes on boost. Obviously you can bypass the solenoid for diagnosis.
All them bits on a hub dyno with E85 should see you making 600rwkw on about 28psi give or take. I would keep a stock engine under that somewhere, up to you how crazy you want to go and how gentle your tuner feeds in the power.