The above checking procedure is a load of crap to be honest with a USED engine as the most important area here is the wear on the crank/shells etc, as you can lose it all here.
It is however overlooking one major influential factor and that is the oil you use.
10W40 is WAY TOO THIN, in a worn hard worked engine, personally I wouldn't use this stuff on my door hinges let alone a car engine.
I suggest you try a thicker oil first, tests have shown oil to run at 30C hotter than the engine(water) itself, on average.
The same tests have also shown the biggest problem with some oils was thier complete breakdown under pressure, CASTROL RS being the worst culprit.
I really would not concern yourself with the oil pressure at idle, as no great amount of pressure is needed, I would be more concerned about it as boost starts, as this puts the crank in particular under increased load.
It is all very well FORD quoting oil pressure, but we live in the real world.
Another point may be the accuracy of the oil pressure gauge/sender.
I would not be too quick to do anything, some engines have a LOT less pressure at idle.
Change the oil for Silkolene PRO S 10W50, or if mega high mileage MILLERS 10W60.
tabetha