Can you actually post rc.conf and output from zpool list
, zfs list
and mount
after a reboot (before manually mounting anything).
It's very difficult to provide help if we can't see what your system is doing. You say you have zfs loaded and enabled but we have no way to confirm you haven't made a typo or mistake anywhere.
Regarding the second point, your drive is 6,000,000,000,000 bits. If you keep dividing this by 1024 to work out how many TB it is, you'll find it's approx 5.45TB. This is the same with pretty much all drives and always has been. You also lose a bit due to ZFS using/reserving some of the space.