Great thread, appreciate the insights, everybody. Hope you don't mind if I throw a few thoughts out there...
Just for reference, I'm 42, a guy, with a 2:45 marathon PR that I ran about fifteen years ago. The next year, I got hit by a car - an 84 Yugo! - and it broke three or four bones in my foot. While I got back into running, I never got around to doing another marathon, but with the folly of middle age, I'm thinking about getting back into the game this fall. Also, just happen to be another person with Bay Ridge connections - I lived on 74th St. off 3rd Avenue from 2007-2013. Great neighborhood, and I have fond memories of running on the shore path with the big ships going by in the fog.
To BL: From what you've described, it sounds like your performance in the marathon has been limited by a lack of basic endurance. If you were doing 6 miles for bread-and-butter runs and 16 miles for long runs, then maybe that's not surprising. (I understand that some people do have success with the Hansons' program, but it seems evident that it wasn't doing enough for you on the basic endurance end of things.) If you're able to bump up your bread-and-butter runs to 10 miles, that seems like a big step in the right direction. If you're able to stretch out your long runs to the 20 mile range, and maybe do three of those (or more), that ought to be a big help, too. In fact, I would suggest that if your goal is to get under 3:30, those are probably the two most important things you can do - significantly more important than the details of what you do with your faster-than-MP workouts. Don't get me wrong, it's good to run "comfortably hard" on a regular basis, but you don't need to sweat the details of exactly how you do it. (It's also a good idea to do "speed workouts" - strides, hill sprints, light fartlek - on a regular basis, but you don't need to sweat the details of that too much, either.) In fact, for someone in your situation, I would put the priority on running more miles, and then do the quality workouts that you are able to do without compromising your mileage, rather than the other way around. (Note: I'm not suggesting that you try to run as many miles as possible, and I'm not suggesting that you skip the quality workouts entirely, either.)
In general, I do wonder whether you are sweating the details a little too much. Philosophically, I think this is one of the places where I have trouble with the Daniels approach, or at least what seems to frequently be the takeaway from the Daniels approach. On one level, this may be just a personal quirk - I'm not really a charts and numbers guy - but on another level I do think there are times when it works better to focus relatively more on feel and effort and less on specific times. It can be a good thing to run a little scared, but you don't want to run worried.
Just my two cents, and of course, different approaches work better for different people.