Couple of questions/problems. Including low Oil Pressure

Alright to start 2001 4.0 120K

First question on the clutch fan. I was told it was suppost to be hard to move after the car had been warmed up and mine is rather easy to move both cold and after being warmed up....time to replace?

Biggest problem is low oil pressure. At highway RPM's 2100 I sit around 33PSI with 20w50 oil at idle I get around 10. This is with a mopar filter backed up by a mechanical guage. At startup I get right at 40PSI. I know this is close to spec but with 20w50 I figure I should be getting better pressure at cold startup. Im waiting to see if I can get it to hit zero pressure again. I have a new sending unit on the engine as well. I figure bad bearings but anyone think it might be the oil pump slowly going out? The last time I did the oil change myself with 20w50 about 5 months and 15K miles ago I was gettin nearly 60 PSI at startup. The JiffyLUBE has done the ones inbetween then and now and were supposedly using 20w50 as well.

Also if it ends up being a bad motor does anyone know if a late model 4.0 from a TJ will swap into the 01 XJ? I figure I could find a low mileage TJ motor for allot cheaper than rebuilding or getting remanufactured.

Forgot to add I've looked into the valve cover and have seen no evidence of coolent leak into there. Though I do have a coolent leak i believe its from a bad radiator as opposed to a cracked head.

I've owned it since it had 30K on it and it has overheated before due to low coolent but only for a second. Temp now sits right at 210 no matter what the oil pressure is. No knocking or anything.

Thanks for the help and look forward to learning.