1. Lots of flying during the summer months. You'll be flown about every day on Reserve during the busy seasons. I'm not on Reserve anymore, so I can't speak for the "off" months. OO runs a pretty lean operation (staffing wise).
2. Lately it has been 4 day trips and Stand-Ups (take the last flight out that night and first flight back into base early the next morning). Ironically, I had a better schedule when I was less senior than I am now. You can absolutely fly as much as you want, within 117 of course. My bid award for Sept was 89 credit as a junior FO, and I didn't bid for any increased flying above minimum (75).
3. Yes, ATL is all 200. The 700/900 fly through ATL but they are not operated by ATL based crews. Flying is holding flat now. ATL base exploded but has now seemed to reach appropriate staffing levels. A little more flying may be coming before all the XJet flying is gone.

Probably never. There's no reason for the ERJ to come to ATL - Delta controls everything, so there's no real competition in ATL, and therefore no reason to bring a new, efficient airplane down here. Plus OO already has 700/900s that fly through ATL.