Hi J-DUBBED, If you and your wife can control your emotions and actions and change your thinking, you might be able to improve your relationship with your son. If you read Steven Hassan's books, you will learn that cult members have an authentic persona and cult persona. Your daughter-in-law was indoctrinated just like your son. The problem is the WTBTS - not JWs!
The key to helping your son is to empower his authentic persona so that he can start to critically think for himself again. It will be easier to have a relationship with your son by empowering your son's and his wife's authentic persona. You need to socialize with them doing fun activities where they might be able to meet more non-JWs.
Even your daughter-in-law has an authentic persona. Unfortunately, her authentic persona may be controlling, but you will not know until you ask her simple questions and get to know her.
Peace be with you and everyone, who you love,
Robert