Went above and beyond only to get shafted, how to keep going?

So I have always been an overachiever, I have outstanding reviews from every manager I have ever had and often had to turn down management positions my jobs have wanted to put me in. Even then I have been a manager for several years so I have the experience. All that to lead up to my current job. It isn’t in a field I enjoy but I have a talent for it, the pay is good and honestly not liking a job has never stopped me from being a top performer. I’ve been at this job for 4 years and it is a small 4 person team including the supervisor. And for the past 3.5 years I have done the work of 1.5-3 people as we had people going maternity leave, one who just stopped doing their job, two of the 4 of us quit at the same time, then training the new people while still doing their job of 3 people. Still kept my high stats throughout it all, with all the weird side projects my manager gave me, I still finished everything in a timely manner.

Then our supervisor left and I said, ya know what, I know the job well I will apply. My supervisor left with the recommendation that I take over his role and trained me how to do it. I even took over the spot and did all the work of the supervisor in the 3 months it took for the hiring process, all for them to give it to someone else. They brought me in to tell me that they gave it to the other person because while they have zero experience in the role (or any management as I came to find out) they have a certification I didn’t have, but in 6 more months I would have had it. Then I was also told that they had planned to make a new position to give me so I could still get a raise which is also why they gave it to this other person, only problem was it wasn’t in the budget so HR said no. I am/was utterly crushed so here I am the one who knows the job best under two newer people and I get paid the least.

The new supervisor and manager have been just awful, I have been made to feel stupid as I try to correct them changing things they don’t understand. My life have turned into a hell of micromanaging, multiple useless meetings and I just can’t take it anymore. I am beyond burned out so I have just decided to put in as much effort as my two coworkers do. But now I am getting meetings about my attitude, my attitude is me not talking when I used to do most of the talking. I will let us all sit in the silence, make my coworkers talk I don’t get paid extra so why should I expose myself to get railroaded and belittled by my management.

I already had an exit plan to go back to school in a year and leave but honestly I’m not sure how I’m going to make it that long. My blood pressure is through the roof and a lot of people have come to expect a lot from me and I just can’t do it anymore and now I just feel like a shell of a person.

So any advice for putting up with terrible management, micromanaging and burnout for just a year?