To the op, I understand your pain, but from dealing with AMD and driver bugs especially OpenGL driver bugs, I would exercise patience. I've encounter 2 drivers bugs in the past and having filed reports along with reproducible cases, it took months to get a response on their forums( along the lines of what you are experiencing), but they did eventually fix the bugs. The annoying part was that they did not mentioned it was fixed, I just decided to test my app with the workaround removed and that code path worked without issues.
My advice is that if you have narrowed down the GL calls responsible for the issue, then try to see if there is a vendor extension that capable of doing the same thing. The reason I say this, is that strange enough, the issues I encountered were broken in AMD core OpenGL implementation, but their implementation of the Nvidia vendor extensions worked fine…imagine that.

This is why software dies: The cost of maintenance is not zero, and once the cost of maintenance approaches the possible gains to be still had from the software. the software maintenance will no longer be paid for.

This actually happens for cars, too; manufacturers only keep spares in stock for about 10 years, and after that, if something fancy needs replacement (typically something with a chip in it) you're better off going diving at a scrapyard than trying to buy an original replacement part.