Dr Prius results! magic 8-ball says, outlook not good.....

Just from that info, it sounds to me like your battery is a good candidate for a Prolong, but it's still a bit of a gamble. Is your Fremont in California or Nebraska. If in CA, there may be someone in your vicinity who could loan or rent you theirs and then you'd only have to buy a cable for it to see if it helps. If it helps, then maybe spring for a Prolong. If it doesn't help, you won't be out as much money.

 

It comes down to the most basic question... How long did you plan to keep the car ?

Here in Minnesota, where the seasonal changes push people to replace at that point anyway, it's an easier decision.

 

I agree that the decision should take into account what your long term goals/plans for the vehicle are.
You say you bought it cheap, last May, knowing the battery was suspect.
Basically Dr. Prius app results included, nothing has really changed. You still own a soon to be 14 year old Prius with 220K miles on it, and a Hybrid Battery that is suspect.

So it's kind of a No Answer, Answer, but I have to ask what do you want to do?
I'm not saying this is your case, but sometimes I think people know what they want to do, but will end up at Prius Chat asking the community what they think they should do, really looking for validation or permission to do what they want to do.

If I'm reading your post correctly, you've narrowed it down to these options.
Replace blocks 11-12 and buying a prolong system.
or
Replacing the battery at newpriusbatteries. com. My understanding is that these are Battery Kits, and require a level of DIY investment.

Both options come with risk, and cost.

But it all leads back to what do you want to do?
Some people really want to DIY. In which case replacing battery blocks, and using the prolong system is just part of the "hobby" or the journey they really wish to take.
Even the battery kit, represents a desire to DIY.

I think if you are aware of the risks, rewards, of either choice, than either choice is valid.
I would say the prolong choice? Is what it's named. At best? You replace the battery blocks, use the system, and get X more life out of the existing battery. Hopefully prolonging it's life.
Obviously replacing the battery is more an attempt to add significant life to NOT having to worry about the battery. But I haven't got much direct long term feedback about the success or failure of these battery kits. Just saying I don't know here. But you're NOT buying a brand new OEM battery. So I would say, there is some risk in going this alternative route. Maybe others can offer better feedback about this specific choice. But ultimately...

The choice is yours.

 

I believe @Raytheeagle is in that area with the Prolong system? If you choose to replace the battery, the kit of new cells from @2k1Toaster here is cheaper than a Toyota battery. The link is in my signature. You can even sell your tired, not yet failed modules to recoup some of the expense.

 

When I moved to the Prime, I gave up my co-ownership.

Now it’s @SFO and @The Critic that pull the trigger on the equipment.

 

What about the Prolong harness? There's some time and expense involved in installing that.

 

Once that’s installed, it’s easy to share.

The equipment sits idle most of the time anyway.

Why not make some good use of it.

 

I am in Clayton, CA so I can certainly meet up with you for the equipment. If you plan to keep the vehicle, a new battery makes a lot more sense. The cost of the dealer batteries is around $1700 w/exchange and is a much better long-term solution if you plan to keep the Gen2 for a long time.