1. No.
2. There are dozens of existing threads discussing DL's future (or lack thereof) in the DL forum.
3. SkySaver Awards:
http://www.delta.com/skymiles/use/sk...t_us/index.jsp
(It's 25k for a domestic reward.) Multiply x2 for SkyChoice Awards.
4. I suggest you review the fare rules on your preferred routes to determine whether stopovers are free.