Nutter, once you figure out why it won't boost with the wastegate disconnected, you should be able to adjust the wastegate preload by turning a set screw on the top of the wastegate, this will raise the "no boost controller" boost up to around 19 psi, then you can use the boost controller to really crank it if need be. If you don't have an adjusting screw for the preload, then the boost controller alone should be able to pull the boost up to 20 or so.
Honestly it sounds like a restriction in the exhaust or a huge boost leak, but with a leak that big, you should hit FC dues to the massive amount of air your turbo would be sucking. The other possibility would be that your header flange is warped and isn't sealing against the head enough to build boost. I've had a pre-turbo exhaust leak limit me to 6 psi before...
-Jake