I think you made the right decision to delay - retiring safely at your (young!) age, given your current situation and depending on your lifestyle goals may not be a slam dunk now. A couple of comments:
Be very wary of the Firecalc results!! I know people that heavily relied on the tool to decide to retire just prior to 2007 and are sorry for it now. Firecalk essentially assumes that future US stock market behavior will be similar to the past. Stock and bond market history for the US might be an historical exception and not necessarily a good harbinger for the future (see research by Dimson et al). Firecalc also implicitly assumes that mean reversion in stock market valuation doesn't exist (future returns are not dependent on today's stock market price levels). While its possible history may repeat itself, and that mean reversion may not be a strong factor, these represent significant uncertainties in my opinion, and I think you should consider simulation models that allow for a range of future market tendencies
. When it comes to modeling the future, its not just the ergodic behavior that is important (the time-dependent fluctuations and return path), but its also parameter uncertainty (the future average return uncertainty and volatility, for example). Firecalc does not address the later, and this is a major flaw in my opinion.
If you are willing to expend a little effort, I recommend reading a book or two by Milevsky, well known economist, insurance expert, and professor at the York University of Toronto. He has developed a very simple analytical model for retirement that allows you to input forward-looking portfolio return average and volatility values, as well as your age and assumptions about mortality. So you can test a number of different possible future outcomes. While not as flexible as Monte Carlo simulation, the model's simplicity requires little effort and will force you to think hard about your retirement assumptions. You may be surprised! Here is a link to his spreadsheet model:http://www.qwema.ca/wordpress/wp-content/uploads/2012/06/7Equations_June1.xlsm
Go to the sheet called "#7 Kolmogorov". You can read about the model in papers he has published and books. The spreadsheet link is associated with the book "The 7 Most Important Equations for your Retirement". Have fun!