Tried filetool.sh -b, it said invalid device. So i formatted the usb and just used the gui in tinycorelinux to make it. Frugal mode, ext2, the only boot options i chose were tce=sda superuser safebackup.
Then rebooted, was able to backup filetool.sh, restarted and the changes i made were there
However i tried editing another file, bootlocal.sh, and running bootlocal.sh -b i get sh not found, so it seems like i can't backup that file in the same way as filetool.sh.
I feel like i am missing part of the picture here.