You can back up your personal files to an external disk with normal file-copying commands (
cp in a Terminal or drag-and-drop with whatever file manager you like). That's normally adequate, unless you do heavy customization of system-wide settings (in
/etc). In a worst-case scenario, you'd re-install Ubuntu and then copy your personal files back.
Clonezilla is a popular backup tool if you want to back up an entire partition or an entire set of partitions. You'll then be able to restore the whole partition much like you could with a
dd backup, but a Clonezilla backup will chew up less disk space and will proceed more quickly, since it won't back up unused sectors from the disk, which a
dd backup will.
As to the MBR, I wouldn't bother. GRUB relies on code in the MBR, but also code elsewhere, so if something goes badly wrong, you might need to use Boot Repair or restore the boot loader manually even if you have an MBR backup. This is likely to be safer, too, since all sorts of things can go wrong if you start mucking with the MBR using
dd and don't know what you're doing. Furthermore, as Three Diag says, you may have an EFI-based installation, in which case you'd want to back up the EFI System Partition (ESP). Aside from the MBR's role holding a protective "partition" in the GPT system, the MBR is unimportant in EFI-mode booting. (That said, I suspect you've got a BIOS-mode installation, given the lack of an ESP in the data you've shown -- but I could be wrong about this.)