I am sorry but there is only course of action that makes any sense for you right now.
Get recommendations from people you trust and see a lawyer asap. Get your ducks in a row. Find out if outing your husband and the AP can hurt you in a financial settlement. If it won't, have at it if it feels right to you. If it feels beneath you, don't. I think that is your choice all the way. But if you are planning to out them to try and end the affair and get him to come home - think long and hard on why you'd want him back. Honestly, at this point, with the way he has behaved for a YEAR? I wouldn't suggest giving him the time of day even if he crawled on his hands and knees back to you. I'd start hardening my heart and moving on ASAP. You deserve 100,000 times better. Try to become as selfish as he is being right now and think ONLY of you and your children and making certain that you do not pay any more than you already have for his horrible choices. Make sure that your lawyer takes very, very, very good care of you and your kids. Do not give him ANY warning what is coming. Follow your attorney's directions to the letter. Document everything - every time she or he contacted you and the content of those communications, every time he took sums out of the family back account - but not for the family, etc. Start building an airtight case. Whether he is in a fog is somewhat irrelevant at this point - he's had a YEAR to come out of it. He's been treating you - the mother of his CHILDREN - cruelly for a YEAR. No fog or unmet needs or whatever the excuse is gives him a pass for that. Start getting MAD. Use that anger to propel you to action. i know right now you are hurting - and I wish I could take that away But as long as you let him play this back and forth game - you don't even START healing. You could already be a year into healing if you'd made him make a choice (and stick to it) way back then. Stop the bleeding and take the decision out of his hands. He's clearly crazy or - maybe he IS on drugs. Either way - that is NOT the person that should be calling the shots. We are all here for you.
BS - Female
Married 27 years, one adult child DD May 2016 “When we are no longer able to change a situation, we are challenged to change ourselves.” - V Frankl