Glad they at least gave you a loaner - but you should check out the back brake. You should be able to adjust it - if you're not familiar with how the back brake adjustment works, check out the online agility 50 service manual (you can find it in the General Discussion thread under service manuals).
Driving with the high beam on is no big deal - I do it all the time! The light is so weak to begin with, it doesn't seem to bother anyone.
Let's hope you get your ride back soon.