I guess my next step would be to remove the mbc and just run the hose straight from cooler to gate and see if theres any change.
that should give you basic wastgate pressure of about 5-6psi (below .5bar)
How is the mbc conected directly to the wastegate? I'd think you would have to use a hose.
Check All connections again make sure they are all zip tied or clamped really tight. triple check the blocked hose as well.
What was the set up before you installed this? factory solenoid as in the OP pics?
then maybe return it to stock to see if there is any difference and make sure the two stage solenoid is working as normal, 5psi then 7psi (close to .5bar) This will show that you can get boost higher then the gate spring.
And show us some more pics, might be able to spot something.