honestly? I wouldn't give him the letter..it is not the way you've written it so much as the fact that you've written it.
I know you're not happy with the way things seem right now but is there a way for you to elicit a change without writing such a letter or having an equally in depth converstaion?
what are some things that h is doing right?
can you focus on those and help them to grow?
what are some things that you are doing right?
can you do more in that area?
what are the specific things that you see h doing "wrong"?
what ways could you aproach those areas without as Mellanie says "putting him on the defensive"?