Marathon training, week 7

Training for Twin Cities Marathon, October 9:

Monday: Off.
Tuesday: 10 total. This was the week I switched to the longer, slower repeats I'll be doing for the remainder of the training cycle. Rather than run on the track, I did my mile repeats in the park. It was dark when I started, and I didn't have my backlight on, so I struggled a tad with paces at first. The workout was 6x1 mile with 400m active rest. It seemed very easy, too easy, and my pace was much faster than it should have been (more like 7:05): 6:59, 6:51, 7:00, 6:52, 7:02, 6:50. Hm. No way this could come back to bite me, right?
Wednesday: 8 in the blazing sun at 7:55 pace. Bad idea. First, my workout was too fast. Then, my easy day - the most important easy day, between two hard days - was faster than prescribed. 
Thursday: And Thursday was payback time. I headed out for a tempo, and at mile three and a half, I bonked. Just like the end of a marathon. It was incredibly humid, and I'd gone to bed hungry and didn't eat that morning, but I really think the bonk was from veering off my training plan as far as paces go. I jogged back home for 8.5 total.
Friday: Off. I was scheduled for 8 easy, but I took off because I was worried that Thursday's bonk was a sign of overtraining. Plus, I had to take a final that morning. It was poor timing, because this was the first week with a long run of 16 miles, which is supposed to be on tired legs, but oh well. 
Saturday: 16 at 7:47 pace with 20 levee hills. I keep doing a lot of my runs on the levee, and I have no idea why. It's broiling out there. As soon as I hit the park, the shade under the trees changed everything. My last two or three miles were the fastest because I was in the park. I felt fine for this run, which was a relief, but I'd rather have the experience of a long run on tired legs like the plan calls for. I still kind of feel like this plan isn't working well for me - but maybe with the longer speed work and increasing length of easy runs between hard days, I need to go back to a full day off between speed work and tempo. The tempos just seem harder than they ought to. The pace I am running them at matches my fitness based on recent races, so why so tough?
Sunday: 8 easy.

Total: 51 miles.

This should have been 61 miles - so the workout I quit plus the skipped day had a big impact. I feel kind of bad about that, but I also think that a bonk bad enough to quit a workout should be followed by a day off. Plus, the final exam schedule really gave me no choice (unless I took it late Friday after our dinner reservations). Regardless, I feel like a big failure for flopping on the week. 

Have you ever bonked on a workout? What did you do, and did you take time off after?