I remember reading somewhere that, to maximize your health, run as much as you can each week, you won't hit the upper bound when it gets bad.
In the example you cited, that's 36 hours (!) of runnning in a week: meaning I'd have to run 6 hours a day and only take Sunday off each week before I was officially running too much. And I've noticed I can't run more than 4 days a week anyway, so even that's off limits. 6 hours a day, 6 days a week, even under optimal conditions, wouldn't be something I'd approach even if I was retired.
So practically speaking, "run as much as you can before your body aches stops you" seems like a good rule of thumb.
I'm not sure what math you're using. 12.9 MET for running * 3 hours * 60 minutes/hour is 2322 MET-minutes, so just 3 hours of running is sufficient to exceed the 2200 threshold. 36 hours of running would be 27864 MET-minutes, of course it is too much. But 3 hours of running in a week is quite easy to exceed, e.g. if you run half an hour every morning.
There are some studies which suggest that the artery buildup from frequent running is not bad, but these don't take cancer or other factors into account - in contrast all-cause mortality is one of the most comprehensive statistics available. The drawback is that although it gives you a number, that number might be affected by unknown variables.
MET-minutes seem to be "Metabolic equivalent of task" minutes [1]. In the paper, they give running an MET of 8 (paragraph 3 of Data Analysis section), so 2200 MET-minutes of running would be 2200/8 = 275 minutes, if I understand correctly.
In the example you cited, that's 36 hours (!) of runnning in a week: meaning I'd have to run 6 hours a day and only take Sunday off each week before I was officially running too much. And I've noticed I can't run more than 4 days a week anyway, so even that's off limits. 6 hours a day, 6 days a week, even under optimal conditions, wouldn't be something I'd approach even if I was retired.
So practically speaking, "run as much as you can before your body aches stops you" seems like a good rule of thumb.