Just to keep you updated:
I figured out that i have a huge problem with the space inside my housing.
The switches use nearly all the free room above the circuit board so i have to re-do everything on a new board. I dont want to build another housing because i like the relatively slim one (and it´s already finished).
At the moment i´m using the footswitch on rehearsals and it works fine (except the LEDs and the display which are not connected yet). If anybody wants to do a similiar project without any indicators, its really simple.
I will try to get the simple on/off LEDs to work in the next step. Unfortunately i don´t have much time right now so it will definitely be finished after the arrival of my remote. Maybe i will use the Kemper protocol instead of MIDI if it is possible somehow.