I'm glad you are feeling a little better. Sounds like your daughter did exactly the right thing. You should be proud of her. My husband accused me of involving the children, but when you break up a family the children are involved. So the way I saw it, he involved the kids first.
It is difficult to rebuild the trust,but as you sense, it is necessary. Your husband needs to give you assurances that you believe, and he has to follow through. This really is a test of the marriage. It takes effort on both parts to pass the test.