If there are fireworks and loud noises happening on her street, then that could definately be the reason for the shaking scared rabbit. I guess it's a bit late now... but in the future, maybe moving the rabbit indoors temporarily if he's outside into a quieter area, or making sure he has lots of places to hide if he's scared and doesn't feel too exposed. Also you friend could try covering his cage or enclosure with a sheet or towel to block off any strange lights from the fireworks that may be scary as well.
About the teeth - is the rabbit in any kind of pain - is it eating properly? What is it eating? Does it get unlimited hay? These are all questions to ask your friend. If she isn't educated on proper rabbit nutrition, then you should help her to learn about it - maybe direct her to this site so she can get more information. If the teeth look rotten, she may want to take it to the vet to get it looked at because who knows what other issues may go along with the rotting teeth (eg. infections, other dental issues). It may only be a matter of time before the bun goes into stasis if it's not eating right.
Hope this helps.
Nadia
