Thanks a lot for your detailed description, easelec! I would have never find this out, I was sticked too much with that same-channel-for receive-and-send-concept in my head. Thanks again, it really worked! 
Unfortunately my installed plugins don´t show up within the Loopy Pro mixer when open as an AUV3 instance in the effect slot of AUM but this is another problem …
I hope some day Loopy Pro will work with Studiomux directly. But it feels much better just to see AUM and having Studiomux (technology) in the background.