I think leaving your current job is going to addon further burden to your financial woes, no? Since your boss and colleagues are good so far, seems like they're reasonable people.

Although you mention 8am-5pm is your work hours, how late do you work? I suggest sleeping even earlier (ie. 10pm) if you're worn out from the day's work.

If you have been working late everyday due to huge workload and stress, discuss with your superior on the problems you're facing and see if there's anything he can do about it. Sometimes they can be flexible and make certain arrangement to ease you until you're more used to the work assigned. By simply resigning without talking to your superior is not a good idea (unless he/ she is a terrible person).

To be honest, it doesn't matter if you feel you're not "living up to their expectation" because everyone takes time to adapt and adjust especially in the first 3-6 months. It's a new environment and new work processes and they will understand it. So I suggest not give up so soon and give it another try after talking to your superior and see how things goes. The job market isn't too stable right now, so don't make rash decision unless you've secured another better opportunity elsewhere.

Just my 2 cents worth of opinion. Sorry to hear what you went through previously, but don't let it get to you. Find ways to stand up again and rebuild your life step-by-step. There's a lot more the world has to offer than gloom and doom. You just need to meet the right people to point you the right direction and show you some hope.