Your car is Polo 9n3 like your username?
I can only tell about Mk4 where the cluster is basically the minigateway for can which you dont need.
There are cars out there running 1.8t me7 + dq250 + shifter in a mk1 chassis without cluster, gateway or abs.
Does the torque reported from the ecu in block 120 match with the tcu torque?
Maybe you can re-wire and isolate the ecu+tcu+shifter from the rest of the canbus just for a test?
So far the car drives ok, but there is a decent delay between requesting a downshift and the ECU/TCU actually performing it.
Is this delay much bigger than any stock dsg car?