the idea of uncovering a fuel port due to low fuel is examined in the aircraft manual. while I didn't fly the MD80, I did fly the earlier, shorter DC9...simply put if the fuel is less than 500 lbs in each wing tank a go around must NOT be attempted due to unporting of the fuel intakes.
even attempting an approach with less than 1000lbs in each wing tank is to be addressed as something to be dealt with in the QRH. And a go around with this amount of fuel is to be done with a shallow pitch up and not the normal pitch attitude.
having said this...even with 45 minutes of fuel, the total fuel on board would be closer to 5000plus pounds total (2500lbs per wing)and you wouldn't be close to a problem.
In this type of plane, you use the center tanks first (except for takeoff)