At a loss 2016 Premier

I've been trying to fix this car for two weeks now and I feel like I find a new issue each time. What prompted me to start working on it was a propulsion power reduced message during a long drive in 100+ weather that turned into engine unavailable and engine coolant tempts 230+

Things I've done: Cleaned both the EGR Valve and Cooler Replaced the downstream O2 Sensor (These first two things is what the dealership told me was the problem)

Replaced the 12v battery after discovering it was dead with an Everlast AGM H5 680 because the original was dead

Replaced the oil pressure solenoid (had a mechanic do this) because that code came back after the 12v battery replacement.

It drove fine after that for about 4 days then I just got all of the same issues again with reduced engine power then it went engine unavailable while I drove.