The XMc-2 controller and XM-2 sound module are designed to work with two upper sets of keys and a pedal board. So when you connect it to your organ it works fine.
Midi is sent to the controller – the controller sends midi to the sound module.

I do not own tis unit so this is “Guess work”.
If the controller is receiving three different midi singles, Upper keys, Lower keys, and the pedal board and sending them to the sound module that means it is receiving on three different channels. The organ is sending three different sets of data on one midi channel to the two units, and as you say it works.
Then your job is to find how your organ is doing this. If I remember correctly you can send more than one midi single through a single channel; meaning that you can send 16 midi channels through the send midi channel one. (Possibly more)

This next step is difficult without having the unit.

If you have determined that the organ is using Channel one and sending three different midi singles on that channel – Then you must select the same channels on your Kn7 keyboard and send them out on channel one. Midi out to the units.

I think of midi very much like a garden hose, or better still an electric wire. The water starts somewhere and it must end up somewhere. I can water three bushes in different places with one water hose by use a water controller.

This unit does not seem to work like the modules that we are familiar with. It was designed for a single purpose.

John C
If I remember correctly Bernie owns one of these units, he may be the man.