I could be way off base here cipa, but I think there's 2 basic parts to what you are feeling. 1) You need to get it out, vent, let off steam. 2) You need to just put it across to her exactly how you are feeling ... the sheer violation.
Writing the letter and burning it will fulfill 1) but not 2). You might want to consider the possibility that whatever you say now, and how completely how feel you'll be saying it, more details will come up in future that you wish you included. I think it has parallels to what is mentioned in the infidelity chapter of DR - that the betrayed spouse will have many questions to ask and things to say - but that is in a situation where there is remorse and the straying spouse wants to try and work things out.
That is understandable. Whether it is useful ultimately ... I don't know. In keeping with DB-ing, I guess the best you can hope for if you do go ahead is not to have any expectations on her reactions.
I've been reading your posts, keeping silent since I really don't know ifI have anything constructive to add. I'm so sorry it has turned out this way and you're in such pain ...
Me 42 W 39 Married: 11 Jan 1998, T: Since 1992 First Bomb: Sep 2007 Confirmed A/OM: 4 Nov 2007 Kids: D10, S5 Reconciled and together again after (alot of) time and heartbreak. 3rd kid, S, born 2 Jan 2010.