I can relate to so much of your post. Although I am not yet divorced we have been very civil in the past, including intimacy up until about three months ago (separated ~ 9 mo').
Halloween is her BD and yesterday was tough. Weddings, like you, also totally get me down. I can very much imagine being in your shoes after our D - wondering why it can not work.
Seems as if you two get along well and should continue on with your path of communication. I have read various sources that suggest anywhere from 6-20% of divorces end up in re-marriage.
Me: 48 Ex-W: 45 M: Nov '96, together since Oct 93 Bomb: on 10-yr anni - Nov '06 OM Separated: mid-Feb '07 Divorced mid-July '08 One daughter - 28 XW living w/OM