An idea:
you asked two questions, yet nobody here seems to care about answering the first one.
From what I have observed, shalom bayis is alive and well in most frum homes.
As for the second question. what hurts most?
*Incompatibility.
*Some people just can’t get along with others, so it wouldn’t make a diff who they married.
*Never being taught to handle life’s challanges effectively.