(1) Did you measure the rail pressure while you had the return line directed into a bucket?

(2) Have you looked for rust inside the tank to see why the fuel is orange? (Irrelevant to the pressure problem)

I sense there is a problem with the concept of the fuel rail. The fuel rail is just the wide metal pipe portion of the system between the hose that comes from the filter and the regulator. The pressure within the rail is regulated by allowing the excess to flow back to the tank, so your question about the rail being clogged indicates a lack of this understanding. It would be the return line that is clogged, not the rail.

You should be able to blow through the return line and hear it at the fuel tank cap.

The difference between the two Bosch regulators that fit that rail is a minor detail compared with the high pressure you are reading on your gauge. Assuming you have used the gauge on your Honda, you would know the gauge is not lying to you.

The capability of the "LH Pump" is limited internally by a bypass valve, but that pressure is well above its expected operating pressure. The pump can easily sustain that bypass pressure if the supply voltage is within its specified tolerance. If you deadhead the pump -- which is what I think you are doing with the clogged return line -- the pressure will be as you see it, limited by this internal bypass.

--
Art Benstein near Baltimore

What engineers say and what they mean by it:
"Serious, but not insurmountable, problems."
It will take a miracle. God should be the program manager.