Is applying to 13 colleges too much?

Well, 13 is a bit much. Maybe you could take out some of the more selective colleges because, no offense, your gpa is not the greatest. Even with an SAT retake, your score may not be up to par. I'd say the most you want is eight. Look carefully at the different programs. If you know what areas you are interested in, find the ones that excel in that. Good luck with everything!