First Batch Done

Well I just completed my first batch of Root Beer.Considering it was my first attempt ever at brewing anything, I suppose I'd call it a success,however I have a few observations & questions.
1) It needed more carbonation. possibly not letting it sit long enough? or maybe too little air space in bottle?(pet) I left about 11/4" air space.Added the yeast when mixture was at 85 degrees. Used champagne yeast.
2)I would prefer a stronger heavier root beer.not sure how to accomplish this. Tad more extract? I use malto dextrin.

1. Just let it sit out a little longer. Since you're using PET, you can squeeze the bottles to check pressure. Even now, you could take the bottle out of the fridge and let it ferment some more.
2. More extract means more flavor. I'll make 3 gallons of root beer using a "4-gallon" bottle of extract and reduce the sugar by 1/4 so it isn't too sweet. Birch beer, I only make 2 gallons.

One other question. Can I reuse the pet bottle caps even thought the seals have been broken or do you have to get new caps each time?

nice work
this is typical when making RB for the 1st time

here are a few things to try:
hydrate the yeast in slightly warm water for a few minutes before using
try using a single sweetener
pitch a starter
let it room ferment a bit longer

yes you can reuse caps as long as they still seal
you can also make RB without yeast if you understand CO2 etc.
enjoy