Only you know what's right for you. If I were in your position, though, I'd absolutely leave. There is a wide world of well-paying, very interesting, dev jobs out there that are also at great places to work.

Suffering in order to maximize income is, for me, a bad deal. You can enjoy life and make very good money even if it's not technically the most money you can possibly make.

> now I feel like my skills are degrading.

For me, speaking purely from a professional point of view, this is completely unacceptable. You need to be increasing your skills over time. If they're degrading, you're setting yourself up for a career disaster later on.