I read your post twice and really can't figure out why you are even questioning if you can. Seems to me like you are more than ready. I know more than a few people who don't put in the miles you put in and run 3:20.
Like Ryan said you are running like 57 mpw, you should be totally fine.
BTW I am not a big fan of the race predictors. I only bring it up because you mentioned your 5k time. It can be fun to look at, and can be a measure of fitness, but if you ask me it has nothing to do with a marathon. For example I have run a 19:40 5K and a 41:40 10K (both in the last 9 months) and according to McMillan that should make a something like a 3:15 marathoner. It doesn't and I am not. In fact, I am not even close. My advice (crappy advice as it may be) is to trust in what you have learned from your experience, trust in the massive amount of training you have done, and use those to gauge your goal. Pace predictors are fun, experience will tell you the truth.