since he says 10PSI at idle and the stock gauge doesnt have numbers, ill assume he already checked it with a real gauge.
what you have are classic symptoms of a pooped engine. its time for a rebuild, and as stated, a new pump will only be a band-aid. another band-aid would be to run a higher weight engine oil. this could get you by for a little longer. you start damaging bearings at about 6-8PSI...so your getting very close.
it might also be worth your time to pull the pan and check the oil pickup screen. these have been known to get plugged up with RTV and gasket material over time. i doubt this is a problem in your case though since you have good pressure on cold start-up.
where you go from here is up to you. you can:
A. run it until it eats a bearing, then throw in a junkyard motor. or:
B. STOP driving the truck before you ruin the engine and make it harder/more expensive to rebuild...and rebuild it.
