Re: Should I stay?
Stay, go, or.......another option.
You mentioned others who are not happy; consider forming a "study group", in which you and other students could meet and train. Yes, appointing or nominating a senior student to lead class would be required.
The goal, I think, would be continue your (and your fellow classmates) training in a less hostile environment, until a more permanent solution can be found. A Judo dojo or a MMA group will likely be sympathetic to your plight, and allow you to use their space in the off-hours for a nominal fee. Hopefully.
The choice of whether to keep training at your old home dojo while pursuing the study group remains in the hands of each individual, but I mention the idea of the group as a means of hope and possible growth in an otherwise bleak situation.
What is clear from your post, in my view, is that the Sensei leaving and the sucky people skills of his replacement are separate issues. Related, but separate.
Good luck, we're rooting for you, even the for the replacement sensei to come to his senses in a timely manner; it could happen.