As opposed to marrying her "for real" and carrying on an affair behind her back while still sleeping with her to produce an legitimate heir?
You could say the FL is scummy too for marrying for money.
She married to save her family, she didn’t ask for money for herself or jewelry or dresses. And they had a contract. Although it was a marriage they both new from the start that it was fake so that he could have his mistress. A marriage in that time is no different from a contract. So they aren’t scummy for having a fake marriage it was a give and take marriage. What makes him scummy was when he fell for her but still was with the other girl. He keep getting jealous of her relationship(although they were just normal friends) and bombarding her private life,and inviting her to banquets. All of those were not part of their deal. That would be considered cheating to his mistress. He said she could have other lovers too but he gets jealous and says mean things when he see her close with someone. So the scummy one is the husband
But then I found out the Male lead was as scummy as dick lint and I dont know how you can get that low. ╮(￣▽￣)╭