You are doing this at 19, no JW wife, no JW kids or grandkids. It might seem tough now, but it could have been a nightmare at some time in the future.
So...now I feel horribly guilty because I've alienated the only two people who really matter to me in life..the only two people I truly love...and I've brought them such grief and misery..
Don't blame yourself for their pain. You did nothing wrong. You didn't ask to be raised in a Jeckle & Hyde cult that treats it's members badly when they leave. You didn't ask to be taught lies. The 'grief and misery' are the result of the cult's teachings, not you. Your mother and GF need to get their shit together and confront their cognitive dissonance, not you.
Welcome to the real world
Chris