You are not alone .... I am so sorry for all the loss you have experienced in such a short period of time . Take some time for yourself to heal emotionally . You may not realize how much of what you are currently going through may be based on the fact you are still in a grieving process over your mother and Sister. I am sorry your Dad has not handled the grief ,maybe it is not too late to work things out with him for mutual support . A local support group could be beneficial too .
As for fading .... it is NOT the easier road . It does make you feel in limbo because you ARE ! You are being pulled in many different ways and pretending to be something you are not . Really give this route some thought and decide, is it truly the best way for you ?
In regards to your family life ,my advice would be to seek family counseling . Or in the very least begin a new way to bring the family together . When my kids were little we had very little money ,so we found every free thing there was to do with kids . We went camping ,found every local park to explore . We found zoos and museums and special community events geared towards families . This helped strengthen our family and gave us time together to explore interests . When you are drawing away from a community based religion such as the JWs you need to replace that sense of belonging with something else . Look for clubs or interests to join that will give you that feeling of being apart of something else and a way to meet new people-friends to introduce into your life .
Good luck with whatever you decide ,and remember you are not alone . Someone to talk to is only a keystroke away .