Again, your oil pressure is not the issue here...and the idle variations seem normal, as there are relays that adjust idle (like when the A/C compressor cycles).
Difficulty with hot starts sounds like the OVP, but since you have had it replaced recently (replacements have been corrected), I am now wondering if it is a fuel-related issue.
You have replaced the ancillary components, so it's not probably that any of them are "seizing" up and causing erratic stalling problems...besides, you would see premature belt failure by now, or at least a lot of belt material coating ther rest of your engine.
Sounds like perhaps there is a vacuum leak of some sort...on or near your fuel distributor.
Also check your ignition components, specifically, the cap, rotor and ignition coil...
2009 ML350 (84K) - Family vehicle
2001 CLK430 Cabriolet (71K) - Wife's car
2005 BMW 645CI (124K) - My daily driver
2012 Mustang V6 (60K) - Daughter's car