i'd definitely say that dentistry could be a good fit (but realize that i'm biased, since i'm just about to start dental school myself)...
1) you do get to work with your patients. you may even be influential enough to change their habits to improve their oral health care which could be pretty satisfying.
2) i don't know any facts about this but read the ADEA report at
http://www.adea.org/DEPR/Assocreptjune01.pdf
it gives pretty good information about the field
3) the average salary statistics I've seen have all been well above 100k, actually around 120-160k or so for general practitioners and around 220k for specialists.
4) you're going to have to arrive at whether being a dentist contributes meaningfully to the lives of others or it doesn't. i imagine most everybody on this forum would say that it is but when all is said and done, it's your opinion that matters the most. except for the most extreme circumstances, i don't think you'd be literally saving people's lives. for the most part, a dentist improves the patient's "quality of life" (for lack of a better term).
5) dental schools are actually really in need of teachers, something that you won't find in regular medicine. so if you'd like to be a professor, the opportunity is there. if you go to the ADEA website, there are actually reports that tell you that the field is in dire need of teachers.
you seem to have figured out where dentistry fits into the rest of your preferences so i won't make arguments for them here.
you definitely need to spend some time with dentists...good luck.