You can use either use the 0-100% expression pedals or modify the sampleset.
The software looks like a better solution than your "busy-loop" thread. It can be used with LD_PRELOAD without modifying software. It a possible option for GO, if it is picked up by the various Linux distributions.
So you are using the organ as speakers? The other option: You could use external speakers directly connected to your PC.
Apart from changing the sampleset, you can use the various enclosures on the float manual panel. There is one for each windchest going from 0 to 100%.
Look at the GO audio/midi settings.
Your audio recoder directory points to c:\ - you can't write to this directory. Please change the audio recorder directory to a writeable directory.
You should look at: https://github.com/FeralInteractive/gamemode
Could you please provide the output of the zypper install command? Regardless, if you use 42.3 or Tumbleweed. OBS automatically builds GO packages compatible with the latest distribution updates. Therefore there can't be any missing or incompatible libraries.