Thanks, that is really helpful in understanding where you're coming from. I have trained at both extremes - as a pure strength athlete (college football offensive tackle), then a pure endurance athlete (raced distances from 5K up to marathon on the "good enough to win my age group at local races" level), and then a hybrid for awhile. It is really tough to do both on a truly high level, so I was trying to figure out if you want to be
a) runner who can go into the weight room without embarrassing himself
b) lifter who can run a few miles alongside hobby-joggers without dying
It sounds like you're a little closer to A than you are to B. Am I correct?
If so, then I think your chosen approach is reasonable (build your running volume while sticking with a 3 day, core-lifts-only program). To be a really fast 10K runner, you'll have to run quite a bit more than 15 miles per week, I'm afraid...I don't know just how fast you're hoping to get (i.e. if you just want to get under 45 minutes, that might happen at 15 miles per week with some judicious use of speed work and a little carryover fitness from your lifting; if you want to get under 40 minutes, that number will have to be somewhat higher, probably 25-30 miles; and if you want to get significantly faster than that...you'll probably need to rethink this whole venture a little).
For what it's worth, I ran a 41-minute 10K in fall 2009 weighing around 205 pounds off a steady diet of 15-20 mile weeks. A couple years later, at my absolute fastest, I ran a 38-minute 10K off more like 45-50 miles per week. All of the people I ran with (who were all faster than me) ran a good deal more than that. Just one anecdote, but gives you an idea of the realistic curve you might expect. Given your description re: the minimal effective dose and 80/20 principle, you'll probably find a sweet spot around that 15-20 miles per week range, which might get you fast enough to not-embarrass yourself but probably should still leave some room to lift as well.