I'd suggest #1. The game is really not too long once you know what you're doing so it shouldn't be tough to get back to where you were, and it'll be a good refresher for the relatively tough DLC. It'll also give you the ability to play around with a different build than the one you went with initially. The DLC is balanced really well for a NG playthrough so I'd advise going that route over NG+.
Probably best to start from scratch and then play the DLC when you get to BL 65-70. I wouldn't recommend doing the DLC for the first time on NG+, especially if you've been gone for so long.
My first run through The Old Hunters was in NG++ and I had been playing the game non-stop since release, it still kicked my ass. The hardest bosses and areas are in the DLC.
If you decide to go through it with your old save, at least make sure you're not over-leveled as it ruins the experience.
Allright, new game it is! Thanks for the insight, good to hear the DLC isn't too easy or too hard for NG.