
It seems that plant shops almost reflexively blame all plant problems on overwatering. I agree with your assessment that it has been underwatered. However, repotting it will not address that problem.
Keep it in that pot. Tamp the soil down tight around the edges of the soil. Then, let the pot sit in several inches of water for a couple of hours so that the water is wicked up from the bottom and the soil gets re-saturated.
After that, water it slowly from the top whenever the top surface of the soil feels dry to the touch. The rest of the soil will remain damp and will be better able to absorb normal watering.
Also keep your FLF close to a sunny, uncovered window.