First of all, although you can't run the course completely unimpeded, you can come pretty close, particularly when it is early on a Sunday morning. There's the Framingam Route 126 intersection, Natick Center, Weston Road, Centre St, Washington Square, Coolidge Corner, and Kenmore Square. With a little luck, you can get through almost all of htose unimpeded. The remaining intersections can usually be blown through due to light volume, crossing to a particular side of the street, or more luck. Really it's not that hard to do the whole course with only a couple of stops.
In 2003 I did something almost identical to what you did and it was just about the dumbest thing I could have done. At the time, 2:52 was my PR and I was shooting for 2:40 at Boston. My other races indicated that was a realistic goal. But on a cool day with perfect conditions, I ran a 2:51:xx on the Boston course, start line to finish line. I was an idiot, but I didn't learn that until later.
My plan was to go easy until we hit the hills and then hammer up those. That was it. Instead I started with a group of folks who run hard all the time and right off the bat we were doing 6:30s. But for some reason I felt like a million bucks. The run was only supposed to be 23 miles but I just could not bring myself to stop. Unlike you, I knew where the mile markers were and how fast I was going. That was why I decided to keep going.
I remember finishing and thinking I might even run close to 2:30 on marathon day. Yeah, right. About 3 or 4 weeks later, I "raced" the marathon in 3:01. And that damn near killed me.
You have the advantage of about 3-4 weeks more recovery time than I had. And maybe you are more resilient. But if you are not trolling, I would advise you to go nice and easy for the next 2 weeks - actually watch your pace. Beyond that, I have no advice to offer. I've never run that stupidly in training since so I don't know how to do it and recovery.