You can use the terminal command "dd" to create a backup of the whole MBR including boot loader and partition table.
The MBR is in the first 512 byte of the disk. Boot loader makes up the first 446 bytes, partition table the next 64 bytes, followed by 2 final bytes of the Magic Number. See Wikipedia for more enlightenment.
Backup the MBR into file:
sudo dd if=/dev/diskX of=/PATH/TO/BACKUP/diskX-mbr.bin bs=512 count=1
Restore: Swap the paths after "if=" and "of=":
sudo dd if=/PATH/TO/BACKUP/diskX-mbr.bin of=/dev/diskX bs=512 count=1
Restore only the partition table:
sudo dd if=/PATH/TO/BACKUP/diskX-mbr.bin of=/dev/sdX bs=1 count=64 skip=446 seek=446
You need an admin password for the "sudo" commands.
The backup file can be named other than "diskX-mbr.bin". If you are experimenting, it's very wise to include date and time in it.
To find out the disk number use:
diskutil list
This method works from any OS with a terminal (the disk labelling may vary), from the active system, and even through ssh (search for "dd through ssh").
I am sure.
No idea about boot loader settings, though, sorry.