When you say you backed up boot, was that the efi partition?
The msr partition may not have anything in it. It is unformatted space where Windows virus checkers or DRM software may write serial numbers. Still probably a good idea to backup.
I would not delete any partitions. Some systems need them and you currently do not need the extra space.
If installing in UEFI mode grub should auto install to the efi partition. I think it still shows choices. But if in BIOS mode you still install to sda.