Don't be ashamed that you have worked so hard at this relationship. I think that the journey of relationships and marriage are fraught with confusion, and difficult decision making. You made a difficult and courageous decision to try to love your wife with all of your heart. I think you made a difficult and courageous decision to have your son. But, as you suggest, I think you did it for the wrong reasons.
Children Rarely Add Spark to a Marriage
My understanding is that rarely do children bring people together, they are more likely to rip you apart. Intimacy, romance, passion, are all much harder with young children in the house. Check out my bio to see how hard it is for me and my wife!
You Owe It to Your Son
I believe, though, that now that you have your son, you owe it to him to at least try to fix your marriage. You may be right that you don't love your wife with the passion and fire that you felt for your ex. On the other hand, your ex was bad for you. It is very common for people to be attracted to people who are bad for them and feel that spark, that excitement. It comes, I believe, from internal conflicts that often come out in therapy.
Now, you are also right that therapy cannot manufacture your love for your wife. It may only confirm your feelings that divorce is the best option. I agree that even with children, that a marriage based on love is better than a marriage based on obligation. But don't be hasty. You have a lot riding on this decision, and the life of your son in your hands.
How Open Have You Been With Your Wife?
How open about all of this have you been with your wife? You might find tremendous relief to know that she feels the same way!
If that's true, you will have a strong base to decide where to take things. If you are right that she is "starving emotionally," she may already be wondering how to make this marriage work.
Marriage and parenthood are long term deals. Each day is filled with complications, new challenges, temptations, frustrations, annoyances, drudgery, and routine. On the other hand, it is possible to capture the mystery, excitement, passion, and fun of a dating relationship -- but it takes planning and some work.
It's easy to get stuck in routines that pull you apart. You have to learn how to dance together, again.
I wish you the best of luck whichever way you go. I just wouldn't be impulsive in my decision.