Ok, so, I am able to hook everything up, but I'm probably doing it wrong. I either get poor sound, static, or any other type of irregularity, no matter how I choose to plug everything in.
First I will list my equipment, then I will state something close to what I'm trying to accomplish. Also, I'm aware that some hardware I have may be redundant, and probably doesn't need to be included in my setup.

Equipment:
Synthesizer (Microsoft XL)
Yamaha CP5 stage piano (full range electric piano with midi capabilities)
Boss RC 50 Loop station
Korg Kaossilator Pro+
Mix8 8-channel mixer
Harbinger 4-channel mixer
Steinberg UR44 audio interface (4 preamps, midi in/out, 6 inputs, 4 outputs)
MacBook Pro (I have a DAW, but my issue is with hardware)

(I have more pedals, mics, monitors and synthesizers, but their hookups are straight forward)

What I'm looking to do:
Basically, I want to figure out how to be able to play both keyboards and the Kaossilator in a way that I can live record loops on the loop station, and send the audio to my audio interface. I shouldn't even have to use my computer... I should be able to just receive all audio from the interface, right? I want to be able to playback loops, and record new ones on different phases without the loop station from "hearing" the already recorded loops. (This is because I have had issues with the loop station double-recording loops after receiving the inputs from the mixer. I added my second mixer to eliminate this problem, but I am receiving horrible sound, feedback and static)

Is this even possibles? What cords to I need, and where should they plug into? Damn this is frustrating.
What goes where in the interface? What goes where in the mixer? Am I a missing any essential hardware?

Please please please and thanks thanks thanks.


[NOTE: Of my many attempted setups, currently both keyboards are connected to different input channels on the mix8 mixer, the Kaossilator is connected to the mix8 via line out to aux in, the main out of the mix8 goes to the loop station instrument in, loop station out goes to interface in. I'm such a noob, and my ears hurt after every time I put my headphones on. This can't be right. I'm also pretty sure I don't have any bad cords, FYI]

[NOTE 2: I've played piano for 23 of my 28 years on earth. I've gone electric only a couple years ago, and I am obviously struggling)

 

Thanks a lot! I appreciate your response. This is definitely the lead I've been searching for.