It must be so difficult to be a parent who wants to donate to their child and isn't able to because of a medical issue. The process of testing potential donors is meant to exclude anyone who has something in their medical history that would increase the risk of that donor to have an adverse outcome or do more harm to the recipient by exposing them to potential infections or other complications. If this eligibility testing is compromised in any way it will erode the entire system of donor testing. Some conditions put the donor at risk some conditions put the recipient at risk.
Fatty liver is usually divided into two groups depending on cause. Fatty liver from alcohol or non alcoholic fatty liver disease. I am sure you must have read up on this extensively, if not you can google and go onto a website from a major health institution. Here is one website (information purposes only no medical advice).
http://www.hopkinsmedicine.org/healthlibrary/conditions/liver_biliary_and_pancreatic_disorders/nonalcoholic_fatty_liver_disease_134,178/Fatty liver from non alcoholic causes is usually caused by metabolic syndrome, like you mentioned, high blood pressure, high cholesterol, high triglycerides, diabetes. The damage cannot always be reversed, but by controlling blood pressure, cholesterol diabetes you can prevent further damage. Patients with fatty liver disease may go on to develop liver failure. Given this diagnosis you may want to consider seeing a hepatologist (liver specialist) to see what you can do to reduce your risk of damage.
In the meantime, perhaps you can advocate for your son and get the word out that he is in need of a transplant. Someone may want to test who was not aware of the need. Should someone be an eligible donor but not compatible you can research programs for incompatible donors and also exchange programs.
Wishing you and your family all the best.
Sherri