Hi, and congratulations on your already great start!
Personally, since I tend to be fairly moderate-to-conservative in my projections, I'd lean towards using the 8% target or even less. 11% pretty much mirrors the historical U.S. stock market index over all time. So, to achieve that rate of return, you'd have to likely be invested 100% in stocks every year over the next 14 years you have mapped out. I'd likely not have a 401k portfolio that aggressive as I was getting nearer to retirement.
More likely, you might want to be scaling down to become progressively "safer" over the next 14 years of investing, and having only, say, 20-40% in stocks as you get within a couple of years of retiring. The rest would be in less aggressive (i.e., risky) investments.
I think a more reasonable, long-term average rate of return might be closer to 7%.
Also, keep in mind that there are some pretty heavy restrictions about taking money out of a 401k before age 59.5. You can set up SEPP/72(t) withdrawals prior to age 59.5, but there's a limit on what you can access, and it may not quite match MMM's 4% "safe withdrawal rate." You might want to look at directing some of your investments to non-IRA type funds (just make sure to max out that company match on your 401k no matter what!).
For your second question, I'd suggest redoing the calculations at 7%, then get an idea of whether the projected amount will equal 25x your annual budget. If yes, then you are in business!