Moll's marriage to this fool doesn't last too long. He's dishonest and, unlike Lancashire, the ways in which he's dishonest don't seem to match up with the ways in which Moll is dishonest.
Some of his problems stem from the fact that he's caught between two social classes. As Moll says, "at last I found this amphibious creature, this land-water thing called a gentleman-tradesman" (230). In other words, he's not quite a member of the aristocracy, but he's more than just a merchant. He doesn't know which class he should belong to and keeps blending the two categories. He wants to be more like a gentleman but can't really be one from a tradesman's position.
Perhaps this is a sign of the times. Back then England was going through all kinds of social upheaval, and the distinction between classes was becoming more and more blurred. Of course this didn't mean that you could wake up one day and be an aristocrat, but it does mean that you weren't totally stuck with the status you were born with. Still, it was hard to change how others saw you, so it makes sense that this linen-draper finds it difficult to move up. And his shady finances certainly don't help matters.
In any case, Moll has little patience for his behavior and his time in her life is short. He comes and goes in a matter of pages and all he does in the meantime is go through their money and leave her in the lurch.