Ok, did some more testing. The screen before the pump had a couple of small particles in it, but nothing I thought would restrict as much water flow as it has. Cleaned it out anyways, no change. After reading the replies on here and looking at my setup some more, I'm pretty sure I got it figured out. The 90 degree valve by the dump tank valves looks like it closes off the hose that connects to the bottom of the fresh water tank, so that you can bypass the fresh water tank when winterizing it. Makes sense.
I put a bucket of water in there and had the valve so it would suck water from the bucket instead of the tank. Same low pressure. So, to me, that's saying the line from there to the fresh water tank is not the problem (no debris in there). Screen cleaned but made no difference.
Hooked city water up again just for the heck of it, water pressure is great in everything (shower/toilet/sinks).
One thing I did not try, which I didn't think of until just now, is putting my air compressor from the winterization hook up part and seeing if there's any obstructions in that section of hose to where the water pump inlet goes. I will have my wife assist with that.
Assuming that's clear, it has to be the pump. There's nothing else in the system. The pump and everything has already been pulled. Once I figure out the hose is clear, it's just a matter of replacing the pump.
As always...input is always welcome!