I'm new to your sitch, but you sounded like you could use some hugs. I've been there!
I'm not the person to offer advice on detaching. I only accomplished it when I decided I was really done with xBF. After that things were SO much easier for me. I also went completely dark because we do not have children.
You are right, getting off the roller coaster is the step you need to take. I was riding it constantly myself so I understand the toll it takes. Whether or not your H has his own apt should not impact his ability to watch the kids so you can have some time to yourself. I hope there's a way you can make arrangements because GAL is so important to detaching. Once I started doing activities I enjoyed I noticed I wasn't thinking nearly as much about my xBF, OW or the sitch.
Please make an effort to find some time for yourself. I know you're crazy busy but taking care of yourself is the best way to take care of your family. If you're not around or in a good state, how much will that impact the children?
I hope you take this the way it's intended. Just trying to help ease the pain I know you are going through.
If you love somebody, set them free. http://tinyurl.com/2empx2g