Don't know if the shuttles run this time of year, but if they do they run not just in Bar Harbor and the National Park, but also to local camping areas. Last time we were there we camped right on the coast a about 10 minutes from Park headquarters and were able to take the shuttle in.
As for weather - be ready for anything. The first time I went we were there 3 days and saw nothing. It was either raining or foggy. this type weather seems to be common. (I went a second time and enjoyed the views.)
I don't remember any bug problems and so can't help you there.
Ellsworth is a fair size town not far from BH and would have full services.
You should be able to get food in BH - if the shuttle is running that would be easy.
I never tried hanging while there - I've been with the wife and she won't hang