I have been working on a project from a few years. My Manager never appreciates us, but is very quick to find the faults. I have also been yelled upon for the mistakes of others. Last year I had expressed my desire to leave, stating some secondary reasons. I was not allowed to leave. I even wrote to my HR and higher authorities, but, no one went against my Manager's wish to keep me. My Manager told that he would leave me after 3 months. After 3 months, it became some more months, and then some months more further. And now he is trying to further extend me for another year. Here, there is absolutely no appreciation, or praise, for the hard work, I, or my colleagues, put in. But the mistakes (genuine or not) are yelled upon pretty quick followed by angry threats. As far as I am concerned, it has become a point that if there is a group meeting, I would definitely be pointed out, without a reason, and my other colleagues can anticipate that. Another senior, a friend of my Manager, has also started hating me ever since I answered the question he had publicly asked, on the same public platform, which he didn't like. Not a single opportunity is missed to pinpoint a mistake. I even indirectly offered a replacement, which was rejected.
Also, even though we are made to work even on the weekends and festivals, there is absolutely no self-progress, with not enough work, due to which I am getting out of touch with my skills, and my knowledge rusting away. I am also not able to find interviews (trying my best though) with other companies at the moment.
The only benefits I have are extra salary from working overtime (with less allowances) and working from the place of choice (which if I argue a lot may be taken away too), which are not enough without motivation or satisfaction.
Due to this I have started to feel depressed. My manager is trying to extend me in the same project for another year, and I don't know how to say No to him, since writing to HR/Senior authorities does not work. I feel in a deadlock. My colleagues feel in a similar fashion.
Any suggestions? I need help on how to tackle this situation, and leave the project.