I had to do this exact same thing for my now ex-boyfriend. It was much harder than I thought it would be... to put down on paper, for someone else to read, all the heartache we had been through in the two years we were together. I remember not sleeping at all the night I wrote it. I would recommend you sit down to write it in a quiet place, where nothing else will interrupt you, and without any kind of time constraints. There were a lot of tears for me.
Good luck... I hope your boyfriend gets what he deserves from the VA.