The first paragraph of the bootinfoscript tells you
Grub2 (v1.99) is installed in the MBR of /dev/sdb and looks at sector 1 of
the same hard drive for core.img. core.img is at this location and looks
in partition 7 for /boot/grub.
You don't have an sdb7 partition. You show an sda7 partition with btrfs but no boot files? Do you still have Slackware, Gentoo and xp installed along with windows 7? You don't seem to have any Grub2 files except for those on sdc which are your CD or flash drive.
I don't know which boot-repair utility you are referring to but, apparently it just reinstalled windows 7 bootloader to the mbr.
How were you booting previously if you had the other OSs' installed? Grub Legacy? Lilo? Which was the primary bootloader prior to trying to install Ubuntu?