I believe I agree with your summary section:
I think your best option would be to control the two passing sidings (blue and orange) with the Tinman spur control switch. This way you could run two trains on the inner loop, and stop them on either siding to let the other train pass. I would use the spur controller to control the red left and green right switches.
I also think you’d be best off by adding two additional on/off switches for the green and yellow spurs thereby allowing you to park an engine or operate on there with separate power if you wish.
Like you said, just isolate each spur/siding with a fiber pin in the center rail at each switch.
Fun track plan. What did you use create the terrain and ground cover? It looks great.
