That was a strong and obviously very heart-felt letter you wrote him. I doubt much of it will get thru to him right now, but at least you're "on record," right?
From here on out, now that you have spoken your peace, as it were, I'd prefer you give him a much shorter position:
"This is your mess; you need to clean it up."
and
"I've decided I'm no longer willing to lie to cover up your poor decisions."
I do recommend you STAY as COMPLETELY DARK on him as you can at this point. The "friends" thing . . . I'm sorry, but it's not your job to make HIM feel better about his infidelity and deceit.
"Never shelter an adulterer from the consequences of their adultery."
