(a) Step away from the flat iron.
(b) I think a spiral set would look good with your length and thickness. You'd use the same sized rollers you used before, but just roll the hair differently. I started typing out an explanation on how to do a spiral set but the instructions didn't make any sense to me so I know they would not have made any sense to anyone else. Do a search for the poster "prospurr4." She has her hair in a spiral set in her siggy. Your hair is about the same length as hers. I think you'll like your hair like that.