Although this man and Moll seem to have a fairly nice relationship and he supports her for several years, they never marry. When they first meet, Moll says he sounds like a pretty nice guy:
He was a complete gentleman, that must be confessed, and his company was very agreeable to me, as mine, if I might believe him, was to him. He made no professions to be but of an extraordinary respect, and he had such an opinion of my virtue, that, as he often professed, he believed if he should offer anything else, I should reject him with contempt. (410)
Part of the attraction she has to him comes from the way he treats her as so virtuous and noble. Up until now, she's had relationships with so many men (often for money) that his idea of her being virtuous in the first place is nothing if not ironic. Of course that doesn't keep Moll from embarking upon a relationship with him, though. She feels sorry for the guy because he's stuck in a dead-end relationship with an absent wife. Unfortunately, this means that Moll and Mr. Bath can't get married. Never mind the fact that the two have a kid.
By the end of their relationship, though, he's far from being the nice guy he started out as. One day, he tries to just stop showing up. It's the eighteenth-century equivalent of dumping your girlfriend via text message.