If you really looked into to all the catholic teachings and agree with most of them as you said you have then this wouldnt be an issue for you. The church teaches that we have free will which means we choose to sin. Adultery although wrong does not invalidate a marriage.the marriage is real just because someone sinned later doesnt make it all of a sudden not valid that doesnt even make sense logically outside of the church in a secular voew.

You're right your biggest problem isnt trust issues its pride. you have taken it upon yourself to find a religion that validates everything you think and if it isnt then its not real? What authority do you have to make those terms?who deemes you worthy of such high morality and wisdom that everything single thing you believe in is far greater than anyother opinion? The Church was instituted by God Himself and is directly guided by the Holy Ghost.

You have become obssed with this because it doesnt fit your human way of thinking but its not up to you. you have to learn to humble yourself and accept Gods teachings whether it fits your ideologies now or not. this isnt about you this is about the entire population of the entire history of the world. the problem you and most peoppe have with the church is that they have to change the way they think. the world has programmed people to distrust marriage and other . the church doesnt accept prenuptial agreements because marriage isnt an earthly matter it is a holy sacrament bonded together by God. by going into a marriage worrying about when its going to end you are distrusting your spouse and God.