New to me 04 with issues!

An 04 Prius was just given to me in non-running condition. It has a 2 month old 12v battery, but the drive battery has issues. I've been reading around the forum a LOT and know I will have to either delve into the main battery or replace it. I can get a used one for around $850.00 with a 6 month warranty. I'm very mechanically inclined and am comfortable working with high voltages. I've attached a screenshot showing the current voltages of the cells in the main battery. Would it be worth my time to try to get this battery back into shape by rebuilding it or would I be better off just buying a battery that may have issues of its own and having to dig into it anyway? The car currently has a little over 50k miles on it, but has been sitting up for the last 2 years. Thanks in advance for any input!

 

Some background on the car: My brother purchased it late 2019 for $500.00 from a good friend of his that had the car since new. His friend was a judge and used it exclusively to drive from his house to the courthouse each day. He passed it along to his son in 2018 and he allowed dogs in the car. The interior is covered with dog hair and mold currently. Water is getting into the trunk area from somewhere. I plan to figure out where it's getting in, stop it, and then remove the battery before giving the car a thorough cleaning. When my brother purchased the car, he found some melted wiring going to the battery ecu. He purchased a used battery ecu and the harness that was melted, replaced them, and wasn't able to get the car to start after that. Prior to his repair, he was able to start it twice. I've been reading the thread on rehydrating and balancing the battery modules. I believe I'm up to page 12 right now. It looks like something I will probably delve into, if necessary. Looking at the main battery, it appears that some of the contacts are wet on the side of the battery facing the rear of the car. No doubt it needs to be pulled, cleaned, and dried at least, along with the lower case repaint. The liquid appears to have a blue tint to it in places. I still have the original battery ECU and harness, I believe, in the trunk.

Battery readings are currently as follows:
block 1: -0.16v
block 2: 0.65v
block 3: -0.29v
block 4: 13.84v
block 5: 13.14v
block 6: 6.75v
block 7: 7.35v
block 8: 11.68v
block 9: 11.65v
block 10: 0.19v
block 11: 0.25v
block 12: -24.86v
block 13: 24.84v
block 14: 13.86v
HV battery charge: 64kW
HV battery discharge: 64kW

I'm under no illusions that this car will ever be a family trip car. I am just a very curious, and frugal person. I think it will be fun to see what I can get done and how far along I can get this car from the state it is in right now! If I ever get it running, it will only be a maybe twice a week commuter for me.

 

So, I'm guessing I'll just start looking for some Gen 4 nimh packs from a wreck to swap out all of the cells with. The battery itself is far enough away from the leak, so I don't believe it has gotten wet from rain. Hopefully the electronics are alright. The leaks are closer to the rear of the car. I had read a few posts about the roof seams leaking where it transitions, so I'll try to get those cleaned up and re-sealed. Just haven't had a dry day to get to it just yet.

Will the used ECU that my brother bought for this car work or does it have to have the original?

Just the general condition of the car is the reason I am currently thinking it will never be a family car. It is extremely dirty on the inside. However, I know that it can be cleaned and reconditioned to look much better. The front bumper, hood, and rear bumpers all need to be replaced as well, so it really needs a lot of work. My first order of business is to get it sealed up so it can dry out. Clean up the interior. Then get the battery sorted. Lastly, the bumpers and hood.

 

Yeah, I'm fairly certain I'll try some Gen 4 modules before I buy a new pack. This vehicle is strictly a project at this stage. Now, if I get the car back into good enough shape to where I won't be embarrassed to get it out of my driveway, I might look into that option in the future.