How would you bend this frame back?

You need to work on your story. I would tell people that it was from a naked red-head during a photo shoot.
I'd say those hydro lines are magnetized and the roof rails bent towards them and .....caused that car to float in the background. Lol
In all seriousness, I'd take it to a convertible top shop and see what they say. Bets on they've fixed one before and you don't risk ruining it. If the cost is too high for them to fix, they'll probably tell you how'd they do it so you can DIY.