I know he's a bad guy, but my character's a forgiving good guy. Is it possible to get him out of the Legion in one piece?

not sure never had the legion take benny (I played a female char with the black widow perk had six with benny then killed him in his sleep but she is a evil assassin) lol

haha what level do you get that perk

Black Widow opens at L2. I always take it on my Female characters, both for the combat bonus and the additional dialogue options.

If you give him a stealth boy and a bobby pin he should be able to escape but the legion will try and kill you for doing it.