Best thing to do is just leave. If your mom has mental issues (trust me, a lot of JW have), it can only HELP her. You can get professional help but just not having to keep two conflicting ideas in her head will help a lot - I kept my 2 consciences in myself for a while too (the last 6 months) and last week I had a mental breakdown which caused me to denounce this religion, remember past abuse and almost lost my wife and newborn.
Simply leaving makes a LOT of people happier (almost everyone). Simply not having to fight with your own conscience to keep the castle in the clouds alive makes you happier.