Ok..here's my thoughts on the questions.
1. No, not to old.
2. Yes & No. It can help it but that isn't always going to eliminate it.
3. I really don't know about this one. I would just suggest like Nature's Miracle or some other pet odor/stain remover from Petsmart.
4. I wouldn't leave it on him all day. Give him breaks so he can "air" out.
Maybe she can find the time when he is most likely to do it & keep the band on at those times. (I leave one on Lucky at night while we're sleeping)
5. Yes, better to be safe than sorry.
And as far as him going under just make sure they use isoflurone (sp?) gas only on him! And as long as she brushes his teeth often I think he would be fine, but you can have the vet look at them every so often to make sure they are ok. Also if she is going to have him neutered she can get his teeth cleaned at the same time. Hope I am of some help to you!