As long as you pick the seat on the Air France website, the seats should stuck. I have historically had luck with the seats when actually picked on their site. As for Affaires versus BE, somebody posted the links to other posts. Personally, I prefer Delta as I like their food and IFE better, and don't mind the 767 BE seat. Other opinions vary, especially with regard to the seat. I guess it's a question of what is important to you.

Looks like your options on DL would be through ATL, MSP, or SLC.