Damn that is rough to deal with I am not going to lie. I am the same way, like if you feel like the time with me has passed and you done fell for another person let me know. Cause I have no problem with moving on, and when not even her friends know and she is involving the child. Not only does she have no self-respect, she does not respect you or the family for that matter of fact.
At this point it is all about the child, and you seem like a great father, and really care for your son. Terrible that the "Justice System" does not favour men. I do hope the best for you, and terrible that this will alter your education/life. But if you can get even a 24-30 hr a week job, rent out your place and go to school. Try and do it, because you will def need that degree.
Best of luck, and I know its not hard to leave your child's mother after that time, maybe it is for the best.