Be careful what you ask for.
You invited your parents to be your eyes and ears to make sure you were not going to choose another unhealthy boyfriend. I hear alarm bells too. There is a saying in Buddhism, “when you pick up one end of a stick you pick up the other.” The fact that your ex-husband is codependent and that you have a more dominant boyfriend now is actually very predictable. The chances are you chose your first boyfriend because he was so unlike your father, so now the new BF seems like such a refreshing difference. I have written about how these choices are made in my Proof Positive column and you can learn more about this process here and here. Making a completely opposite choice usually leaves us in the same position.
It sounds to me like you need to individuate right now. You are in a very dependent situation, have asked your parents to give you feedback about your intimate choices, are reliant on them financially, and your boyfriend has used what is known as an active-destructive comment with your son. “I bet they are on that table,” after what your son said, would be almost the perfect description of a purposefully hurtful comment. Out of the many other more positive comments or interactions that are possible (e.g., “let me help you find them”), he picked the one designed to be punitive. To learn more about this, click here.
I would strongly recommend individual therapy. Your university should have low- or no-cost options available and the counselors are typically very well trained in working with graduate students in situations similar to yours.
You are obviously an ambitious, thoughtful person. You are sacrificing many other options to make the commitment to graduate school and furthering your career. Put that first. Investing in yourself, individuating, and gaining greater independence for yourself and your son need to get the lion’s share of your time and energy. I am joining the chorus of those near you saying go slow with the relationship.