1) did the 1.50 downgrader app launch? (showed press x to downgrade screen?)
2) you can get the nandtool HERE! at cory1492's site. Also, you install it like any other homebrew app (it should have a eboot.pbp in the download) then just delete the files in the Recovery folder and insert the nandtools files.
This tool accesses F0, doing this has a chance of bricking (like downgrading/recovering/CFW installs) this is a last resort option as the tool is capable of formating your entire nand. With out a backup you'll be screwed! You have been forewarned. ONLY use it to get a backup.