Yeah, I threw in photos at the last minute...glad I did now! I knew from day 1 that they would require a letter from the sponsor...I guess they don't want it to be a surprise when an American shows up on a spouse's doorstep, haha.
As for the green card, I think that technically you're only required to prove your sponsor's British citizenship...but isn't there a section on the app that asks what other nationalities she holds? I probably would have thrown it in there just in case, but I'm sure it will be fine, or they would have asked for it. I myself am dual nationality (US and Canada), and I included my Canadian citizenship certificate as well as my passport.
Here's another weekend coming, and then the holiday, and then the waiting starts again!