I think the issue at hand is what Emrion said in #16 . First investigate and determine what is going on with that data pool (all vdevs show, do they get evicted on a scrub, etc..). Check your ESP partiton on the freebsd boot disk and see what's going on with that BOOTX64.efi . Adjust according to the rescue environment, basically look at ls -l /boot/efi/EFI/BOOT/BOOTX64.efi vs ls -l /boot/loader.efi. Maybe you misremember what you did or not do on that machine.
The point is to get FreeBSD working on that machine. The red thread to follow is: why is the machine all of a sudden (*rolleyes) not booting and gets stuck in efi console when the zfs data pool is attached. Now that you have your data back, there is no stress. You can keep at it and run this down all the way if you want. Best of luck!
Edit: Also look in that loader.conf and disable the microcode if you have it there , reboot and test
The point is to get FreeBSD working on that machine. The red thread to follow is: why is the machine all of a sudden (*rolleyes) not booting and gets stuck in efi console when the zfs data pool is attached. Now that you have your data back, there is no stress. You can keep at it and run this down all the way if you want. Best of luck!
Edit: Also look in that loader.conf and disable the microcode if you have it there , reboot and test