How can I still bring her back from the brink but tell her she needs to stop turning to OM for emotional support and turn to me when we have a hard time getting through to each other on the phone?
You stop "going wobbly" every-other day, and you fight for your marriage and your family. You make her make a choice. Yeah, right now, if you made her make it today, it may not be you. But divorces take time, and that choice won't be made today. They take months, even years if they're contested, depending on what state you live in. During those months, you have a chance eto demonstrate to her what she would be losing, and to work on YOU.
mcol, you need to stop feeling sorry for yourself and steel yourself to fight for your family. I KNOW this sucks. I HAVE BEEN THERE. Infidelity is worse than rape, they say, and I believe it in that it's done to you by someone you love.
You can do this, but you're going to have to go more than ONE DAY with the "Man of Steel" suit on, before going groveling back to the "making her #1" and "I want to thank the OM" stuff. That stuff is absolutely KILLING any attraction she still has for you. If you don't feel like you can do that when you talk or IM with her, then maybe it's best to "go dark" for awhile, although I'm certainly no expert on that subject.