2007 Prius will not start and other issues

I picked up a non-running 2007 Prius with 153k miles for cheap and I'm attempting to get it working properly. I don't have much history on it - the seller bought it from his next-door neighbor's estate sale. He said he drove it home just fine and after he parked it, the brake warning light came on and it never moved after that. He stated that at that time, the only light on the dash was the brake light. He did a very little bit of troubleshooting before selling it. He stated it sat for about 6 months before he sold it to me.

Now, a bunch of lights are lit up on the dash (red triangle, check engine, ABS, etc). I got the Dr. Prius app and it's showing codes P3000 and P0AFA (it also showed P0A84 but I cleared that one after replacing a blown fuse for the HV battery cooling fan and there was one for the battery disconnect not being locked in properly and I cleared that one too). When attempting to shift from park, I get a continuous beep and it will not go into gear.

The Dr. Prius app shows that the HV battery is at 149 V and shows that blocks 1-4 have negative voltage. In the notes it says that all 14 are suspected to have problems. Can a weak battery prevent shifting into gear?

The parking brake switch was bad/going bad (open circuit all the time - I don't think this would explain the brake light staying on) so I replaced it, and the brake pedal switch was also going bad (open circuit on the small wire when the button was pressed) so I replaced that one too. I had some time the other day so I checked every relay I could get my hands on and they are all functioning properly. The brake warning light persists and it will not shift into gear.

The 12 V battery was replaced in May of this year and has 13+ V. I can hear the brake actuator pump operating and the brake pedal feels fine. Plenty of pad left.

In addition to the above issues, I have noticed the following:

Touchscreen display doesn't come on

Electric door locks do not work using fob or switch. Fob turns security system on/off but locks don't respond. The locks work when manually actuated on the door.

Headlights don't come on (running lights and brake lights work).

Rear hatch won't open with the button on the handle - has to be manually opened from the inside.

A/C fan blows but compressor doesn't come on (I have done 0 troubleshooting for this).

The car seems like it's been taken care of - clean engine oil, air filter, new tires, etc.

What should I check next? I called my local Toyota dealership and they said they could charge a HV battery but won't - they will only replace it unless it's a warranty claim and the warranty company says to do it. My concern is that I could spend thousands replacing an HV battery just to have other issues that prevent it from operating properly. I got it cheap enough that HV battery replacement would be worth it to me, if that's what it needs.