Does anyone know of a good place to find stats on such questions as, "How many non-profit organizations provide health insurance benefits to their employees?" United States only, please. Thanks in advance!

Have you tried the Chronicle of Philanthropy? It seems like they recently released survey results on this very topic. If you're in a more specific non-profit sub-field, you may be able to find stats from your relevant national organization as well (i.e., the American Association of Museums, in you're in museums).

Good tip. Unfortunately, the Chronicle's website doesn't give you access to their articles unless you're a subscriber.