Right now, if you get that urge to go, you should go! It does sound like maybe the miralax, at the very least, probably exacerbated things a bit.
You know better than anyone about what your body is telling you...if your regularity has changed since surgery, it is probably related. But that doesn't mean it's permanent! My system was in an uproar during the first week, so let me tell you, hang in there for a few more days, chances are things will calm down soon and your old rhythm will return!

Here's some info on what an abscess is (and a fistula): http://www.fascrs.org/patients/conditions/anal_abscess_fistula/
Did you try eating any bananas? I would really stop the fiber completely right now, and maybe cut back on how much you're eating, as another person suggested. And by stopping the fiber, I mean both supplements and foods high in fiber. Clearly your system was overloaded.
How long did you have your fissure before having surgery?

Eat bananas like CoP said, and cheese, potaoes, rice...be nice to your stomach. Maybe a glass of wine or Coca Cola? Kim always says that too much fibre isn't good and he is right.
Good luck on the interview :)
Corsi