You've made the mistake of believing that you are "part of" the startup. You are just "employed by" the startup - you are not in charge and you can't rely on them for anything. The other side to this equation is you can just quit very easily and get a job somewhere else - you have no responsibility to them other than being professional and seeing out your notice.
Get a job in a bar for a few months, then go back to programming. You're obviously talented - you'll easily get another job.
You've made the mistake of believing that you are "part of" the startup. You are just "employed by" the startup - you are not in charge and you can't rely on them for anything. The other side to this equation is you can just quit very easily and get a job somewhere else - you have no responsibility to them other than being professional and seeing out your notice.
Get a job in a bar for a few months, then go back to programming. You're obviously talented - you'll easily get another job.