There are multiple issues here. As for Plex and k3s, the best solution is to start anew with Docker on Electric Eel, so we might skip that and worry about recovering this pool.
This is not enough to understand what you did and how bad the damage might be.
What commands? For what output?
So you deleted potentially relevant error messages, but do not disclose what these were.
Full hardware description and full output of sudo zpool status and sudo zpool import within triple backticks (``` , </> button) please. lsblk and smartctl -x /dev/sdX for the degraded disk would also be of relevance.