You are well advised to listen to the accumulated wisdom on here.
Many of us have run our Buells from new... getting on for 20 years in some cases. Most of us do not ride like pussies, although it's also true to say that most of us do treat our bikes with a certain amount of 'mechanical sympathy' commensurate with their design and age.
However, the key thing is that we do know the correct tension at which to run these belts. Correctly adjusted, a belt should last for 20,000+ miles. We don't run 'steel' corded belts. Just genuine HD kevlar corded ones.
It is not the problem in your gearbox that has caused your belt to break, over-tensioning the belt has caused the belt to break.
And, more than likely, over-tensioning the belt has caused some problems in your gearbox too.
Hope that clears it up for you.