Leave as planned. You don't owe them anything you scheduled leaving when the app was supposed to be in production. The schedule could keep slipping. Plus your

Leave as planned. You don't owe them anything you scheduled leaving when the app was supposed to be in production. The schedule could keep slipping. Plus your new employer is where you need to keep things positive. That's where your future is. Fellow devs will understand. You will look back on this in 6 months and be thinking why did I even think about hanging around any longer.