Sorry to hear that you are struggling. If you went back for the sake of your elderly mother then keep that at the front of your mind before you make any decisions.
You do not have to accept phone calls and shepherding calls. Be too busy to take their calls or schedule visits. Fade slowly. Miss a meeting here and there and then gradually miss more. Since we are all using tablets etc at meetings you can even read something completely different at the meeting which I have seen many do. Keep your mind occupied.
Terrence O'Brien said at the Australian Royal Commission - "I think Mr Jackson, in his testimony, made the same point as I did in my testimony, that we don't believe it's an impossible choice. A person can stop associating with Jehovah's Witnesses, have nothing to do with Jehovah's Witnesses, without taking the step of disassociation. We've tried to make that very clear." (Day 259 transcript page 26536)
It is possible, it is hard.