Truenas is completely unnecessary, it just brings overhead and complexity. You are good with your setup.

I would advice you to use Gluetun instead of crude Wireguard. Within gluetun you just have to set the port for the qbittorrent’s gui to be accessible locally, and open docker’s firewall for qbittorrent. Then set qbittorrent container to use Gluetun’s network.

There might have been some firmware version messing with cache, ok. But I run latest firmware and yes, my SMART is clean and my scrubs are clean.

I run my 730xd with a H730 in HBA for months and Truenas has never had an issue.