We all make mistakes and the biggest one of all is not to learn from them. The guilt you describe is from someone else's mistake. I was also Catholic and my first wife and i married in a religious ceremony - she was protestant (that actually turned out to be a good thing because I was also able to get this marriage annulled - which is silly now but a big deal then). My biggest guilt was in somewhat bringing up my daughter Catholic (I was starting to see the light on religion so it wasn't heavy handed). My daughter is involved in a mega protestant church but we have a good relationship and I can slowly plant some seeds of doubt. It sounds as if the family is more of a burden on him and a line must be drawn. Religion and guilt go hand-in-hand.

I believed in an approachable God most of my life. Now, closing in on the end of my life, I will leave as an atheist. In all aspects of the living of life, we express life at the level of our understanding. In other words, in our life-long living of life, we are evolving. Even at the times we seem not to be evolving, we are still evolving, in non-evolving. Thus, be thankful for all of your experiences, they've built what you are today. Thus, tell your husband to be grateful for his past foolishness. Atheist blessings.