I spent almost one year in a company where my situation was very much like yours right now. I was constantly frustrated and wanted to quit, but I couldn't because of several reasons. I noticed that such frustration was negatively impacting my work (although no one noticed/cared) * AND * my life outside of work. Once I had that realization, I decided to put an end to it and here's how I did it:

I started using a time tracker. I noticed that if I truly focused, I was able to get all my work done in 3-4 hours instead of 8 hours in a workday. This was amazing because every day, I was done with what was expected from me by the lunch hour. As you would expect, I kept this a secret. Once again, no one noticed anything abnormal as I was delivering with the same pace.

Every lunch hour, I'd quickly eat my lunch and practiced Spanish for 30 minutes. This bumped up my spirits me because I was having fun while learning something new. The next 3-4 hours, I whole-heartedly dedicated the time to sharpen my skills. I was basically reviewing fundamentals, practicing for interviews, and was keeping up with new research in my community. Once I realized I could move, interviewing and leaving the company was very easy.

In hindsight, I think the shift in my mindset occurred after I stopped caring about my then situation and started focusing on where I wanted to be.

I'm in a great place now, but just so you know - the politics, vague requirements, and deadlines still exist :)