Kiff:
You state that she:
"Spends a lot of time away from home and finds excuses to overnight in the City. Claims this is because I am so awful. What if she is drinking?"
Even if she is drinking, did you wonder who she is drinking with. Her saying that you are so awful and then heading off to the city for an evening of fun doesn't sound quite right to me. Maybe she's bored with the married life and "Family games night with the kids" ain't her idea of playing and enjoying the action anymore.
Unless she smells like a brewery and is staggering around the house, from what you have said I think booze is not a major issue if any.