Jules,
Not all selfishness is bad. For example....you could compromise your values and integrity, stay a JW, deal with the resulting depression and drudgery that comes with going but not believing, probably end up getting yourself in trouble.....all while being miserable.
Or you could live an authentic life, reach out to your parents and others with love and positivity, and continue to evole as a person and your belief system.
In the end.....which person better serves their family, their friends, and humanity?
P.S. - I would stay away from the word cult, or other pejorative "triggers". Tell them you have to obey your conscience. You are taking the more difficult road. You simply do not believe they are being chosen. And honestly....I would reconsider disassociating. Give your family a way to speak to you.