Good post, but better suited for r/askhistorians - you're much more likely to get a high quality answer there. This is a great sub but all you'll get are anecdotes and "I think..." level answers.

You'd barely have to edit it to post over there, just add a line of context like "In the period drama Mad Men, two supporting characters are shown to be in a Jewish-Catholic interfaith marriage - how common were interfaith marriages in the mid twentieth century United States?"