Am I wrong to assume that he is the one to tell you? If he did, I believe he is very serious about you and did not want to leave a lie between you, even that early little lie. That is a good thing. Should he feel guilty? absolutely. Should he be punished for life? No. He did the right thing.

If there is no room for forgiveness in a relationship, there is no relationship imo.

I would evaluate his current character and your feelings for who he is now.

FYI: My 41st wedding anniversary is next week.