Just as a thought, examine the hoses leading to the bypass valve. It's possible it's leaking and venting whatever boost you have back into the intake.
That would allow the car to run properly while having absolutely no balls.
Another thought: Stock boost control solenoid? Is there someone with a good one you can swap out for a test?
If that turns out fine, maybe hook the turbo's wastegate cannister up to a bike pump and put pressure through it. I don't know what the stock WRX wastegate spring is set for, but verify the wastegate opens at that pressure. Probably in the ballpark of 6-8psi. If the wastegate arm doesn't move much or at all, then you may have a collapsed spring or other damage and the wastegate might be stuck open, robbing you of boost.
If you're adventurous, you might also consider taking off the downpipe to peek a the flapper valve and verify it.