I need advice please for an issue I believe may have begun with the incorrect ATF put into my 2015 Dodge Durango AWD 4dr Limited Engine: 3.6L V6 24V VVT Flex Fuel (8 speed).

I will not name the retail repair shops....

12/27/24 I had transmission service. I had a Lab Flush, ATF Service Kit, A/T Pan Gasket and Oil Pan Gasket replaced. Then, they refilled the transmission with 7 QTs of DEXRONV1.
10 days later while driving up mountain roads I smelled transmission fluid. Pulled into the parking lot, opened the hood and saw transmission fluid all over the engine. Then saw a trail behind the truck I had it towed to a local shop where the following was diagnosed.

1) Radiator was >1 gallon low on coolant.
2) Transmission was covered in transmission fluid.
3) The transmission was 3 quarts low, and it was black. Cleaned both areas, and topped off both.
4) After running the vehicle for several hours and driving on the highway they found the transmission fluid leaking from between the engine and transmission. Could be either 1) the front pump or the torque converter seal. Further disassembly needed for further inspection. (Declined)
5) Transmission slipping and would not go into gear. There could be internal transmission damage or excessive wear from running low on fluid.
6) The receipt from the original repair showed they used DEXRON V1, which the new shop said was incorrect. That my engine requires Chrysler (Mopar) ZF transmission fluid. The shop said they would never put DEX into my 8 speed...

I went to the original shop and showed them the notes. They told me their supplier (big corporation) recommended generic DEX as the recommended ATF. Therefore, it was concluded that they were following recommended specs from their supplier and have no fault.

I've been reading spec recommendations from the internet and everything I'm reading is my engine requires a fluid formulated for ZF 8-speed transmissions, which is not the same as generic DEXRON. Using a generic DEXRON in an 8-speed Durango could potentially harm the transmission due to improper friction characteristics.

So, what the hell do I do? The two shops don't agree, and now I'm stuck with it.

And for the mechanics out there, how could driving 10 days with incorrect fluid (assuming it's incorrect) cause that much damage to the transmission? And why would it be black so soon?

Is there anything I'm not doing, or should be doing here to try to find out if there is any fault with using supposed incorrect ATF, and if it could cause this much damage? I'd like to find any ideas to resolve this, without making a fool of myself.

Let me know any advice you have.

Thanks.