He is right the turbo need to come to get to the front bolt on the bracket, Sound like you guy at the garage has never fitted on to a k03 turbo before, he would have known it was a turbo off job.
But as for a flimsy bracket?? IMO they have not done summat right when fitting it. And as for trying to fit the oem bracket to the Forge unit there is no point at all.
First make sure they have fitted the spring right.
To set the actuator up you need to make sure the polar axis of the rod is 90 degrees all around from the base of the actuator, then set the waste gate adjustment in the normal manner by undoing both nuts and pusing the waste gate runner up the road until the waste gate fully shuts, then adjust the pre load on the end nut by turning it 2.5 times, then use the rear nut to tighten it all up. Then check the actuator has got enought pre load on by pulling the rod towards you.