Wondered about that.
I beleive you are correct, somewhere I read that in general no violence to suicide for woman.
Drugs would have been more believable using the Marilyn Monroe technique. But then the value of his house would drop a couple of hundred thousand. Small town police have little to no experience dealing with suicide/murder situations.
I suspect this guy is pure evil. He probably planted his daughter's missing items in Mary's bureau. He's ready to move on and marry his actress girlfriend and the church won't give him another annulment.