Moni

I would check for mites or scale before you throw the tree out. If you are seeing fresh green growth on the tips of the branches, then it may not be a lost cause yet. Check for mites by holding a piece of white paper under the branches and give the branches a little shake. If black spots land on the paper, wipe them with your hand and if they leave red streaks, it is mites. Scales look like small bumps that can be anywhere from brown to white in color. If they rub off easily, it is scale.
It still could be a watering problem. I would gently remove the plant from the pot and check to see if the roots are nice and white. If they are brown and soggy, you have been overwatering.
But leave it outside. It is still nice in Florida and the plant hasn't had a chance to adapt to your outside yet.
Moni