My ex agreed to pay for all college expenses when we divorced. (I haven't worked in 25 years) He is now trying to exclude this and exclude that... I get alimony but not enough to help out. My ex is Physician and makes over $1 mil. Year! Can my 19 y/o sue his dad to force him to pay?

Your attorney needs to go back to court and have the judge order him to pay. If this was incorporated into your divorce settlement paperwork that he was to pay for son's college, then by not paying he's in violation of the terms of divorce. You can also have your attorney file for attorney's fees in this matter as he is not abiding by the dicorce agreement.