Idle problem might be a "surging" from what you describe. This can be caused by a vacuum leak, most likely with one or more of the little vacuum hoses. The air mass sensor may also contribute to this. Check for cracks and/or leaks around the intake hoses just aft of the air cleaner.
The oil pressure needle pegging at "3" usually means a bad sender. Just replaced mine last month for the same issue.
Not sure about the temperature gauge, but I believe that would be the temp sensor. Should be on the coolant pump housing.
Can't comment on the ASR as I don't have that light come on typically...
What I'd like to know is did these symptoms occur simultaneously, or is this just an accumulation of problems?
I ask because it really sounds like a bad main wiring harness. I don't remember what years they were deemed defective, but the insulation would deteriorate and expose the wiring...needless to say, you can imagine what havoc that can create!
You may have some bad ancillary harnesses as well, and they may have contributed to some shorting, that would inevitably fry the sensors attached to them (i.e. temp sensor, oil sender, etc.)
Also, don't be in a hurry to fault the throttle actuator...that is one expensive puppy to replace!
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