I can't muster up sympathy for someone who married under false pretenses. (male or female) And especially, put their spouse through counselling and trying to work on a marriage while all along she wasn't being honest with him as to what was the problem. That is just cruel.
If she has any character at all, she will be honest with him, in a gentle way where she takes full responsibility for subjecting him and their child to this. He should at least know the person he is dealing with, IMHO.
So how, or even can she, tell him the real reason she is unhappy? It would break his heart.
Wow, what does she think she is doing to him now?
Think about it...your spouse knows there is something fundamentally wrong with your marriage and doesn't tell you. You just spin wheels trying to figure out what is wrong. THAT is heartbreaking.
She isn't doing him any favors, she isn't saving him from pain. She is selfishly not facing the truth because the truth reveals something inherently wrong with her, not him.
In my experience, people don't withhold the whole truth primarily to shelter the other spouse from pain, but because they get to hold the cards...they still have all of the choices because the spouse is spending all of their energy trying to figure out how they can save the marriage and make the unhappy spouse happy. If she reveals this truth about herself, that she has been lying their whole marriage, suddenly he holds the cards and decides the fate. Suddenly, he sees the real person he is dealing with, a not so nice person who has been dishonest and isn't the person he thought he married. He will learn that she never even really gave him the opportunity to decide if this marriage is really worth trying to save. If this woman is worth trying to make happy.
It's not about whether this guy is attractive or not, obviously he isn't Quasimodo (the OP clarified that it isn't that there is something wrong with him)
It's about this wife's inability to be honest in her relationship...even before the marriage started.
No one wants to know their spouse doesn't find them attractive. But imagine, they withhold that info from you and allow you to keep trying to jump through hoops for a spouse who doesn't share the same fundamental feelings? They allow you to keep trying hard to save something that they never even completely immersed themselves in anyways, from the word go. How much of a betrayal is that?