Fear of committing kufr

Q: I am getting married and I am worried about Imaan and kufr. Since I heard that nikah will be nullified if one of the two did kufr, what precautions should one take?

Is it kufr to like kuffaar daily life ways? E.g. If someone wears kuffar clothes like pants and shirt, if we praise that person by saying that they are looking pretty in this dress, so is this kufr? There are many kuffaar thing which people have adopted nowadays and my husband to be is a duniyadar. Please guide. 

Marrying a man who touched one's mother with lust

Q: I got a proposal from a good, religious man. Ten years ago he once touched my mothers hand with a sinful/lustful intention not more than that. And my mom did not get to know about his intentions. He immediately repented and did not do that again. At that time he didn't know that he will be proposing to me.

If I marry this person, will our marriage be valid or not. It happened ten years ago. Also, now everyone knows that I'm getting married to him and it's so hard to leave each other and to convince our families.