Please know that if you are feeling hopeless, like you are a failure, and that there is no recovering, there are people who will help you. You are not your job or your accomplishments, you are worth it and there are people who love you and will help you. In the Bay Area, call (415) 781-0500 to talk with someone who can help. http://www.sfsuicide.org/
This. 100% this. While I've been fortunate enough to not be in a position of job stress like this, the moment I realised that who I am is not defined by my job was the moment life (both inside AND outside of work) became so much easier.
Edit, to elaborate: take that higher-paying job but less 'prestigious' company because who the fuck cares. Clock out of work on time and refuse consistent unpaid over overtime. Work not doing what you want it to, leave and find something better. Quit defining yourself by your employer and instead work on you.