I spent quite some time training in dojos where oh so many things made me unhappy (although the situation was not abusive, no comparison here). I stayed because I wanted the aikido they do there - no other style, no other teachers were of interest to me. In the end, actually right after my nidan test, I came to ask myself: OK, so I've become pretty good at this, at least of some aspects of the art. Was it worth it?
The moment I asked myself the question, it was obvious that it wasn't. So I left. It took me almost a year after that nidan test, but the decision was already made and I had started shopping around for other opportunities. Until you actually want them, you won't see the opportunities around.
I've learned some important lessons, and one of them is to choose places where I'm happy, where people around me interacts with me in ways I like, and avoid the opposite. I'm trying to use that in other parts of my life too. I've spent way too much time accepting and adapting things and situations that made me shrink rather than grow.
So I say good for you... good for you that you are making this decision. You won't regret it. Life is full of opportunities.
And if you do leave...just go. Don't discuss, don't explain, don't return calls, don't make or respond to contact. Go and stay away.
That's the easiest way - and it's hard enough as it is, isn't it? so why choose more complicated ways. There is no need for you to explain to your sensei why you are leaving.
Here's a text by Rob Redmond, called How to quit a karate club
. His context is karate but all the relevant parts of the text apply.