While I can understand his side of things, he had two chances to tell you the truth up front. Before you communicated, and after you asked him point blank. Both times he hedged. I would tend to look at this kind of rationalization as manipulative and avoid someone who engaged in it.

I sympathize with the guy. Truly. We are sometimes bound in circumstances beyond our control. Still, to me it is a measure of good character not to draw others unwittingly into those circumstances.

It's a shame that he either didn't wait until his divorce was final to start dating or that he didn't disclose the whole story to you up front. You have to make your own choice on this. I would hesitate. When a marriage ends emotionally is not when a marriage ends.