Tldr: follow these instructions from Leandro Glossman to get a trusted self-signed Thunderbolt driver that supports the MacBook Pro. When I looked into Thunderbolt in general, this fix surfaced quickly.
I had been trying to get a TB 10Gbe network adapter working and had been focusing on troubleshooting the adapter itself.
After weeks of troubleshooting, I finally found a solution that seems to be working.
I cannot believe how much of a pain it has been to get Thunderbolt devices to work properly in Windows on a MacBook Pro.
