Codes P0172and P0175, engine does not rev up a few seconds at cold start

Vehicle always started up by revving up to around 12-1,400 RPMs for a few seconds and idle down to normal 7-800 RPM. I know that was normal. Now even at cold startup my vehicle only revs up to 9-1,000 RPMs or sometime only rev to 7-800 RPMs. Also, after a long drive and I turn the engine off and let it sit for about 10-20 minutes, then it starts at low 3-400 RPMs for about 2-4 seconds and then levels to 6-750 RPMs. I have codes P0300 Multiple Cylinder Misfire, and sometime P0172 Fuel Trim System Rich (Bank 1) and P0175 Fuel Trim System Rich (Bank 2).

I have changed oil and filter, fuel filter, PCV value, checked and cleaned the MAF, checked all vacuum air hoses and tighten all air clamps of what I know or could fine, my next steps are to change the Coolant Temperature Sensor even the live data is showing temp is ranging from 75 degree when cold and up to 188-190 degree when driving, and, I was thinking about changing the Idle Air Control valve hoping this has something to do with sending the throttle and ECM communicating to advance pedal position to accommodate the air, gas, and temp at startup. It will be cold in ND soon and I'm thinking I will have cold starting problems.

I have plans to for P0300 and rich none burned gas escaping at a later time because live data is show fuel trims are ranging from -18 to -28 when idling and -5 to -18 and sometime -28 when revving to 15-2,500 RPMs.

I am only concerned with the startup issue for now. What directions can you give me? Am I’m approaching the startup issue in somewhat is a right way?

I will appreciate your thoughts.

Thanks