I am very sorry for the difficulties your family is going through right now. In order to help offer potential solutions, here are a couple of clarifying questions:
What is your son’s GPA now?
Am I understanding correctly that the father is supposed to pay 1/3, you’re supposed to pay 1/3 (and you have 529 funds sufficient to do so), and that your son is supposed to pay 1/3? Or are all of these 1/3 of the UMass costs? So if UMass-Amherst costs about $31k, that the father would pay a little over $10k, you would pay a little over $10k, and your son would be responsible for paying a little over $10k. Then, if your son went to a university that was more expensive than UMass-Amherst, that the difference would need to come from scholarships or other aid?