Any share that has files (or just even the top level folder) on cache, like the M----s share for example, will say unprotected, since you have a single cache device, set them to cache="yes" and run the mover, so everything is moved to the array.
No need to run a balance, GUI replacement already does that.
Usually yes, but always good to have backups in case something goes wrong.
As you wish, it doesn't make any difference.
If it's not under lspci it's not being detected, so it's not a driver problem, it's hardware, also pretty sure those NIC are already supported by Unraid.
There are csrf_token errors spamming the log due to having multiple browser windows on the GUI, that makes it more difficult to search the log for errors, but as far as I saw everything looks good.
Look for a lost+found folder, any partial/lost files should be there, all the rest should be OK.
Unraid is not a backup, you need to have a backup of anything irreplaceable.
You can do it now, since not much point rebuilding if the filesystem can't be fixed, to use the GUI check you need to set the filesystem on that disk to xfs, you can do that by clicking on it.