Notes
A few data points:
(1) No meaningful HR data. I replaced the battery, and it doesn't seem to have mattered. My HR monitor gives me valid readings when walking or resting, but not when running. Not sure what's up with that.
(2) Accordingly, I was going by feel, which partly explains the slower mile pace; I have a tendency to go a bit slower than I should without a good measure of HR.
(3) I need to update my running schedule. Doing a tempo run on Friday, then cross-training via Ultimate on Saturday, then a long run on Sunday, is just stupid. My legs understandably struggled with that. (This is what kept me from being able to do a good pace when I tried to speed up at mile 12.)
(4) I need to choose pre-run foods much more carefully before a long run; the combination of cheese and summer sausage a few hours earlier proved exceptionally unpleasant – probably too fatty, and my digestive tract did not appreciate it. (This is what kept me from finishing.)
(5) Carrying sufficient water, etc. is difficult. Need a Camelbak. Also, having a couple GUs with me helped a lot, I think.