Don’t test them all. First just disconnect the valve & see if the idle smooths out. If it does then you can busy on it.
I have no idea if this is your issue, but I know its possible b/c I’ve had the problem before.
Finally, OK…Next time it stalls and refuses to start, determine if it is lacking fuel or spark and correct the problem. There is a port on the fuel log to check fuel pressure. 4.2L, must be a V-6, probably with COPs. Checking for spark is a pain in the butt but it can be done…
Are you sure this truck doesn?t have 207K miles instead of 107K? Even with 107K miles it isn?t unusual to have comparatively low oil pressure at idle when warm. The kerosene cleaning was a bad idea and may have increased bearing wear which would cause low idle oil pressure. If your mechanic tells you the pressure is OK I would believe him. If the transmission is a standard you could try raising the idle speed a little or try using slightly heavier weight oil. Customers incorrectly interpreting gauge information is one reason manufacturers stopped providing them.