I just stumbled upon your thread. I feel for you, I truly do. I've been here for 11 months and went through a similar sitch. I'm still going through it. I have no success story to tell in regards to my H and I reconciling. However, I can tell you that I'm a much better person and a lot stronger even though there are days where I feel completely obliterated.
I just want to caution you about sending letters to your H and/or OW. This is NOT going to make things better for you, I guarantee it. If anything, it will probably make H angry and also see you as maybe a tad weak. And, the OW will probably be over joyed by the fact that you are showing YOUR insecurities by taking the time to send those items.
Regarding you showing anger instead of depression - not a good idea. I've been there multiple times and you know what it gets you? It gets you someone (H) who is angry at you back. This is where the fights start and the name calling and him rehashing WHY he left. Be careful of the anger. My suggestion would be to act indifferent. Just be cordial, smile, but don't get overly bubbly. Just act like he's a friend. If this is hard for you, limit the amount of time you spend with him.
How can he be one way one day and another way another day? Because he's confused. I also caution you about the "truth" sometimes (more than not) they'll tell you things that are not true. So, even if he tells you the "truth" you may not be able to believe it is actually the "truth" - does that make sense.
My H's birthday is Thursday - go figure libra men. They have a tendency to set a course and often find it hard to veer off of that course even if they realize it isn't really where they want to be.
I would suggest you make lists weekly of things you want and need to do. Then DO them. Try not to anticipate his calls or visits - you will only be disappointed. And, the biggest things to remember.....
You can NOT make him do anything. He's going to do whatever he wants to do, you have to take care of you and your girls. It's not an easy road ahead. But, I made a lot of mistakes and I wish that I had listened and done what the people on this board suggested. My M might have been in a different place, but the more I learn about my H, reconciliation doesn't seem like the best option for me and my baby anymore.
Hang in there.
M 5yrs 1st baby-girl born 6/18/08 Bomb: 10/13/07 OW - I was 6wks Prego H Moved in w/OW: 11/2/07 D Final 07/10 OW had his baby 3/17/09-so her Me, now - happier than I ever was with him