to back up tyour scores, you just need to backup this directory:
/var/opt/rovio/angrybirds/

theres 2 files inside... copy them to a safe place and you're good to go for when **** happens.

i've already searched the forums, and didnt find anything... i didnt 3starred the whole levels, i had like 80% done... and like i said, playing them all over again could be a real pain.... if i wanna go for the 3 stars anyway... cuz, passing them is no biggie.