I don't feel I can give you proper advice really as I am trying really hard to work on my own marriage here. I have been on anti-depressants for about 6 months now. I dread the day I have to wean myself off them as I really don't think I will ever be able to make it without the help they give me. My prayers and thoughts will be with you. I'm sending you a big hug also.
Infidelity is painful for all involved.
I know it has completely torn my H's family apart. Though they support me and the kids and believe that what he is doing is wrong, they also tell me to just work on myself that this is his problem. It does not really take the pain away. They tend to simply use it as more fuel. If you haven't sent it, you may want to say all the things you said but in a way that is still loving.