If I may point out that up until a few centuries ago it was perfectly normal to give women away in marriage as soon as they reached the flower of their age. So 12-14. Boys usually 14-16.
The Bible never specifically states a age but that was the norm for pretty much everyone. The whole purpose for marriage was to procreate and spread further. So technically as soon as a woman was able to have kids she was seen as "of age". Pushing that back to 18-20 and even 30s now is a recent development.
Is 12-14 practical now days? No there no reason for it IMO. Should a 40yo hit up a 13 to? Again, not needed now days but it did happen back then and really there is no moral fault as far as the Bible states.
20 with 40 is well beyond reasonable. Both adults.
Just figured that if we were going to moral fag about it I would point out that morally there is no wrong in what Dan would do so long as he remained married to her.