@Chuck1969,
Well, we just can't tell you if he wants out of his marriage. (We also don't know for a fact how often he is having sex with his wife -- he may be telling the truth about that, but then again he might not be.)
If you're interested in a more stable, long-term relationship with him, then I think you should go ahead and broach the subject. If you're worried that it might scare him off, you can start general and oblique and then follow cues.
If you find out that he enjoys the sex but doesn't really want to leave his marriage, then what?
(Remember there may be reasons beyond happiness that he doesn't want to leave his marriage -- scandal, effect on children, identity [right now he publicly identifies as straight], etc.)