Good evening, all.
I've dug through the forums here, and Googled everything else I could find, but couldn't find a thread with these exact symptoms; similar, but not quite.
If anyone has thoughts or suggestions, I would appreciate hearing them, and thank you in advance.

Car: 2011 G37x sedan with 180k miles. Only modification is a self-installed 4-pin trailer light plug that has been there for years.
Executive summary of issue: Started yesterday on the interstate that I simultaneously significantly lost power and ability to accelerate and the cruise "set" light began flashing.
Details of the issue and what I've done so far:

• First occurrence
  • Going about 75 mph on the interstate, for about 30 minutes or so, yesterday when I felt the throttle become mostly unresponsive. Even floored, it would not go over about 2k rpms and have very little power. At the same time the cruise control set light began flashing.
    • No warning signs/symptoms before this happened. This is my daily driving and it had been running great.
  • I got it off at the next exit, turned the car off and restarted it right away and immediately had the same acceleration lack of power
  • I pulled over again and let it sit for about 5 minutes while I did a quick google search on my phone. This time it accelerated and had power like normal for about 1 minute, then went back to low power.
  • No fault codes generated per my OBD2 reader
  • Drove it about a half-hour the rest of the way home and started research on the issue.
• What I've tried
  • Pulled the brake light pedal switch and confirmed good continuity when actuating the plunger
    • after re-installing I confirmed that when I manually operated the plunger with my finger that the brake lights would turn off and on like they should
  • Cleaned throttle bodies
  • Cleaned MAF sensors
  • Cleaned MAP sensor
  • Checked air filters
  • Checked every vacuum line I could find
  • Checked rear lights (saw this as an issue on YouTube causing voltage issues)
  • Checked battery connections and grounds
• Second occurrence
  • Drove it for about a half an hour on side roads without issue
  • Got up on the highway and within about 10 minutes at highway speed the cruise set light started flashing again and lost acceleration (same as before, wouldn't rev over 2k and no power)
  • When it started acting up this time, I just kept driving and the issue would come and go. Meaning it would lose power then the power would come back, then go away again.
  • I kept driving, turning on and off every switch in the car trying to correlate it to anything, i.e., light switches, seat heaters, blinkers, you name it.
  • tried pulling the brake pedal up with my foot just to make sure it was making contact with the plungers (I didn't do any adjustments when I checked the switch for continuity)
  • shifted into neutral and the engine would rev
  • shifted to auto-manual mode and it would rev more than it would in "D" but still no pulling power.
  • After just a few more minutes of driving it quit coming and going and was just consistently bad, i.e., it was just very low power all the time.
  • After I got off the highway I limped it over to the grocery store and when I came back out 10 minutes later it was accelerating fine.
• I have a Bluetooth OBD2 tool coming in the morning and I have put Torque Engine Management Pro app on my phone so I can see what is happening in real-time

Any feedback would be greatly appreciated.