First the easy bit. If your sonicwall doesn’t support dynamic boot files, you might consider installing dnsmasq on your FOG server to supply the dhcp options 66 and 67 via the ProxyDHCP protocol. I have a tutorial for it here: https://forums.fogproject.org/topic/12796/installing-dnsmasq-on-your-fog-server The tutorial is centos/rhel centric but just replace the yum command with apt-get and the rest should be easy to follow. It takes about 10 minutes start to finish to set it up. Its well worth the effort so you can dynamically boot both uefi and bios systems without having to update your dhcp server.
Since you are just starting out with UEFI, you need to be aware that you can not install (and expect it to boot) a bios captured image onto a uefi based computer. The same holds true for a uefi captured image, it won’t boot on a bios based computer. On my campus I have a bios and uefi base image (2) that are built exactly alike. One for uefi and one for bios.
For the partclone error, the developers would really like to see a clear snapshot of the error message taken with a mobile phone. The context of the error is almost as important as the error itself.
One other thing since you are first starting out with uefi. I see you have dell computers. There is a known and documented issue with linux, uefi, and Dell computers where the hard disk mode is Raid-On. The issue is that linux will not be able to see the disk behind the disk controller. If you switch the disk mode to ahci mode (assuming that you are not using disks in a raid configuration) it will image properly. You can leave the disk mode ahci or switch it back after imaging, but before windows OOBE first boots. That decision is yours.
The error on the screen (in the picture) appears to be during some kind of post install script. Is that correct?