2004 Saturn Ion 2 - AF23 auto transmission stuck in 5th

My 2004 Ion 2 is showing some weird transmission behavior.

It's very sluggish off the line in drive. Giving it more gas just makes the RPMs flare up while the car takes its time getting up to speed. Reverse behaves normally.

Just replaced the front hubs prior to experiencing the issue, but I think the timing is just coincidental.

I was using a brake pedal depressor and left it engaged the whole time which drained the battery. My first thought was that it wiped or scrambled the shift adapt tables. After charging the battery, the starter wouldn't spin so I gave the starter a couple raps with a breaker bar. That didn't do anything and the battery just needed a deeper charge. I also thought that I may have damaged a wire in a nearby harness when I was tapping on the starter. Like I said, I think it's just a coincidence the transmission flaked out right after the hub job, but I don't want to leave out any details.

I was experiencing sporadic hard shifting in the days leading up to this.
The check engine light is on, but it's been on -- I think due to an EVAP leak caused by a crap quality Dorman fuel line kit -- so I don't know exactly when it first threw the transmission codes.

I have a Tech2 and got several codes.
Trans codes
P1779 Torque Delivered Signal
P1781 Engine Torque Signal Circuit
Engine codes
P0700 Transmission Control System
P1700 TCM requested MIL
P0455 EVAP leak
P0141 HO2S Heater Performance Sensor 2
P0128 ECT below thermostat regulating temp
P0113 Intake Air Temp Sensor Circuit High Voltage
P0038 HO2S Heater Control Circuit High Voltage Sensor 2
P0037 HO2S Heater Control Circuit Low Voltage Sensor 2

I think only the first 4 codes are relevant. P0700 and P1700 seem to just indicate that the TCM is telling the ECM there's a problem and to turn the MIL on. The real culprits seem to be P1779 and P1781.

I also observed on the Tech2 that the "Commanded Gear" was almost always stuck in 5th. Sometimes it would show 4th gear for a second or two after shifting between park/neutral and drive, but then go back to 5th right away. It will engage 2nd gear if I put it in low range. It seems the car is just in 5th gear from a standstill, which is why it's so sluggish. Nothing seems to be slipping other than the torque converter doing what it does. Trans fluid temperature seems fine.

I found I was able to use the Tech2 to manually force it to shift through all the gears and everything seemed to operate just fine. No bad noises, shakes, lurches, excessive heat, smells. It seems like there is not any sort of base transmission issue. It seems to be an electrical/electronic problem.

P1779 and P1781 involve the ECM and TCM sharing info about engine torque over the CAN bus. The ECM reports engine torque to the TCM and the TCM can send a request to the ECM to reduce engine torque during a shift to make the shift smoother (and probably reduce clutch wear?). So there's been some sort of breakdown in the communication between the engine and transmission modules regarding engine torque.

According to the manual, one of the actions taken when P1781 is set is the TCM will "Maintain current gear". If the code was set when the car was in 5th, that probably explains why it's stuck in 5th now.

I have a factory service manual and will attempt to go through the diagnostic procedures, but I'm hoping someone on the forum may have seen this issue before and could help me skip some steps. I don't have an indoor shop space and it's cold right now here in the Upper Midwest, so the less time spent chasing a diagnosis, the better!

Thanks, and wish me luck!