"major depressive disorder" may be a bit extreme, but it sure does sound like at least mild depression -- this guy has an easy 8-hour a day job, but still feels overwhelmed by life. He is unable to feel pleasure from playing with his daughter. It's just not normal to be totally wiped out by such a short workday, to the point of being unable to relate to other people.

He's unhappy, over a long period of time, and unable to experience pleasure from things he should enjoy. That's dysthymia. Why begrudge him the chance to feel ok? Treatment might very well do the trick, and make him a better husband and father.