Do that. Get a new job. Never stay in a toxic work situation if you can get out. You will find it hard to believe how much better you will feel once you get out of the shitty workplace.
I've been in not quite the same, but a similarly blocked and disrespectful situation with an employer and it was totally demoralising—I made the mistake of sticking around for an extra year to try to help someone I was loyal to who was very embattled.
I would not bother with attempting a fix internal to the same organisation unless the circumstances are special, like being seconded to a different city or different division or office altogether. Don't palliate too much with holidays and therapy, it just leaves you where you started in the end.
Reach out to a few senior people you've known professionally who you think have a good impression of you (for example the senior staff you mention who've moved on?). The people who are most sympathetic and most networked.
Let them know you've decided to move on and ask for advice, contacts and references. It's very important not to show much fragility in those sorts of talks, because you have to remain clear that you are perfectly whole and ready to give your full effort to a new situation. On the other hand, lots of people you know through work are likely to have been in the same sort of place at some stage, and will understand. If someone does do you a favour at this point, keep in touch and show some loyalty and friendship.
