First welcome!
The problem I see is that since you spoke to both your mother & your sister, they have their 2 witnesses if they really want to hold a JC they can.
WAC's advice is dead on. Is there a local example of something that wasn't done "properly" and that you could use as a source of your frustrations? Or is there someone in the hall that has been "stumbling you"? Or, you said that your dad left and was an elder so you could say that you were thinking about that and it caused you to temporarily have some doubts but your taking the course that WAC suggested.
Then, if this blows over and you fade, try to move to a KH that doesn't have family (if that's possible). Having a relative on the BOE can be either very good (to make things go away) or very bad depending on your relationship with that person. If this is your mother's brother, he's probably hypersensitive to "apostacy" given that his brother-in-law went that route.
Good luck!