This is a very very old thread, which I posted over 10 years ago now. The numbers are completely off at this point. To answer your questions briefly:
1. people can do a variety of things, but in general neurology professors in academic neurology departments do not teach neuroscience courses for medical students.
2. no. in general these teaching positions are filled by PhDs.
3. no. full time teaching positions pay very little and it rarely matters what your degree is. It may be as low as 50-70k with benefits, and in general less than 100k except at very senior levels. MDs who opt for this type of career generally either retired from a full time clinical position or for one reason or another couldn't do a full time clinical job.
part time teaching jobs are somewhat more plentiful, however, they pay even less. Usually they pay between 3-6k a course per semester. So an adjunct professor of neuroscience on a full time schedule of 4/4 at several schools teaching med school/undergrad neuroscience (a fairly typical arrangement) is about ~ 50k on a 1099.