Originally Posted by Wryker
The main cable line comes into an external box (our house is circa 1915 so very old) and at the box it splits up. I don't know what splitter is inside the box. The cable is further split from there but I can't follow all the lines so there is no doubt signal degradation. There is a line in the living room (with a power booster provided by comcast); a line in our bedroom (that's connected to a DVR) another line in another room (currently not connected/in-use) and another line out to our guest house that's not in-use (but will be once we get the floor refinished and walls painted). The NIM100's are pass-throughs - they do not alter the signal in any way - just a way to get ethernet running over the lines so there is no configuration for the boxes (nor should be needed). This just shipped to me:4 PACK Eagle Aspen Satellite Diplexer Signal Combiner & Splitters, D2200 so I'll play around with those (and I'll try combo's of using the current splitter and/or the ones on the way).
Don't take it the wrong way...but ewww...that is what I was afraid of. What you describe here isn't exactly what is on your diagram.
I will assume that the NIM-100s are all set for the same frequency.
I will assume that the NIM was not connected to the living room drop with the amp (MoCA will not pass through most (if any) amps).
What I would do is this and this is exactly how I set my first MoCA network up.
You will need a splitter and some RG-6 patch cable.
I would take the splitter and connect each NIM to an output of the splitter and verify that you can make the NIMs see each other in that little self-contained environment. This way you can verify that the NIMs are working correctly without any variables from your "production" environment causing problems. If you can make the NIMs see each other in the "lab" environment, then the problem is in your house wiring (which wouldn't be surprising given what you have told us.)
Remember this is a standalone coax network for testing, do not connect it to your house wiring until you are sure the NIMs are working. I will attach a quick and dirty diagram describing the test setup.
Edit: Added Test/Lab Diagram