Good article. I like the question at the end. That's good advice for any relationship.
With regard to the sexual orientation question, I've distilled it to something much more simple. "Is he/she not straight?" If the answer is "yes", then you have the information you need.
Trying to accurately characterize our in-denial spouses as "bi", "gay", "lesbian", "pansexual", "fluid", "curious" etc. is a waste of time. They will probably fight wearing any of those labels, and they might not even know for sure themselves. It's an exercise in stabbing Jell-O. "Not straight" is usually the only conclusion you need, and it's a lot easier to reach it.