RE: Smoking, Boston tends to be mostly small ~5 unit buildings so specifically seeking out a "smoke free community" may not get you too far. I would just focus on finding a few places you like, then evaluating the smoking situation on a case by case basis. I don't think it will be too hard to find a smoke free building.

Cambridge is just across the river from Back Bay, and may be a good option to consider in your price range. There are many neighborhoods with great ethnic restaurants, groceries to walk to. Commuting to Back Bay, you would probably want to look somewhere near Central or Harvard, which have a bus line running every 10-15 minutes down Mass ave to Back Bay. These areas do have a lot of students and young professionals, but there are also some quieter areas around there where families live such as Cambridgeport or between Inman and Harvard Square.