Just read your post from start to finish and it mirrors my sitch almost completely. The way it plays out from early in the year to now is just how mine was and is. Your perception of early progress, the drip-drip-drip decline of your relationship, the gradual increase in importance of the once 'just good friend' OM and finally onto the 'I'm done' statement. Everything that has happened to me since January.
I know where you are man. I'm feeling the same things you're feeling. I still have not given up hope but with everyday that passes I feel it slipping further and further away.
Only we can make the decision when to stop this and finally move on. The scary bit is not knowing whether we could move back again if things changed.
FF999
Me 48 W 49 D19, S17, D14 Together 25yr, Married 22yr Me checked-out July 10, back Sept 10 W checked out Nov 10 Separated Dec 10 ILYBNILWY 2nd Apr 11 We're finished + D bomb 17th Apr 11