twicetrader,
I am sorry that you are having issues after the SSD upgrade. I am sure you had hoped the upgrade would go smoothly.
Even though I do not have a direct solution to your particular combination of items, I want to share with you my successful SSD conversion project in some detail because my situation falls into what you called “100% tested and stable.”
[Mac I have]
It is a 2013 Mac Pro with D500x2, 12-core, and 128GB of RAM with an OEM 1TB SSD.
[SSD selection]
I bought a “Samsung 970 EVO PLUS M.2 2280 2TB PCIe Gen 3.0 x4, NVMe 1.3 V-NAND 3-bit MLC Int” from Newegg selling it on eBay. They are still selling it for $329.99, which I think is a very god price from a reputable company.
As you correctly pointed out, I was nervous about FW. The moment the SSD arrived, I looked at the box for “Date of Manufacture”. And, I recall I was happy to see a late 2020 date. At that moment, I was reasonably confident that this SSD swap would go well.
[SSD adapter]
I used a Sintech NGFF M.2 nVME SSD Adapter Card ($14.99) from Amazon.
[Heat Sink]
I used am EKWB EK-M.2 NVMe Heatsink ($17.75) from Amazon.
So, after the SSD swap, I connected to my Mac Pro an external SSD that had cloned contents of the OEM SSD. Sure enough, my Mac booted into the external SSD. At that moment, the Samsung 970 EVO PLUS was recognized and I proceeded to format it for Mac use. I believe I did this swap in mid December. Ever since my Mac Pro sees to run snappier and definitely stably.
In terms of OS on the new SSD, I fresh-installed macOS Big Sur. And, it has been running flawlessly. So, overall, I am very glad that I did this SSD upgrade that I had thought about for many months.
And, I am now flirting with the idea of upgrading the SSD to a 4TB Sabrent Rocket SSD. It is quite expensive, however.
I am not certain if my story would be of any help in your KP situation. But, I truly hope that you will be able to get out of your current situation.
Best wishes!!