I can identify somewhat with your situation, although, I suppose, mine was not nearly as serious as a marriage of mixed religion. My ex inlaws were dogmatic in thier faith and never accepted me, though I too was of the same faith, just a different denomination. For 10 years or more, I tried desperately to fit in with them. My husband turned a bllind eye and ear to their insults, never making me feel part of the family, but instead defending them. After many years of insults in the 20 year marriage, I finally just quit going to visit them! I divorced him after our daughter left for college, and should have done it much sooner, but was too intimidated.
Your wife is a highly educated and intelligent woman. When two people marry, they are supposed to leave their parents and focus on their union as most important. That means building comfort and trust, even if it means (in my humble opinion), offending the inlaws!
Patty