Regarding the frame rail damage, I use a combination of slide hammer with a variety of different head attachments, hand hammering to keep areas of distortion in check, and some heat applied in specific areas to assist with making a specific area more ductile during shaping. i.e. if I'm slide hammering here and it's distorting over there (in a way I can't control different with hand hammer)then I'll warm up the area here a little where I want to movement, and hopefully to overall distortion is reduced.
I did the same assessment as you. Ultimately, I decided to try and straighten...worst case...I'd then cut it out and rebuilt it if I failed.
Hopefully I've adequately answered your question.... Rob