Hi, and welcome!
You must be in shock. This guy is a real piece of work. People like this are very good liars, and please, do not feel foolish! It's not your fault, it's HIS.
Let's see, he is a cheater, a liar, a hypocrite, possessive and jealous. Oh yes, and cares only for his self-interest.
Throw his stuff in the garbage. As far as sending the love letters, well I would do it, but not for vindictive reasons. His wife deserves to know the TRUTH. Send her a copy of them, with a note if you wish, letting her know that you can't stand to see another woman deceived in this way. You could be saving her a lot of grief.
There are lots of nice guys out there, don't let this experience make you bitter.
Oh yes, and JWs are the same as everyone else. There's the good, the bad, and the VERY ugly.
talesin