Did you patch with (R1) and then boot via app_home/PS3_GAME on the XMB? Plus, how do you know that NFS is booting from the one stored on disc instead of the actual copy you backed up? You may be selecting the wring copy all together.
Yeah you had to run the lvl2 patcher first. Just once, it may freeze your console (it's normal). Depending on the game, you may need a disk (any disk) in the drive. As for what to do after that, I'm not really sure, and I haven't found a tutorial or anything that's helpful. BadKarma's been booting off backups though, so you may want to ask him.
Backin up Black Ops took around 20mins I'd say, but Black Ops is 18gbs...honestly I recorded another video while I waited, I just looked over and it was done.