Interesting set up, thanks for posting it. I'm about the same age and have similar goals and fitness, so it's cool to be able to take a look at someone else's approach. How does this compare with what you've done before?
I like the concept of the 3-week cycle. I monkeyed around with the idea of a two-week set up when I was planning out my own training.
In the big picture, it looks like a good mix of different kinds of work, and I imagine it could work well for you. However, my own inclination would be to turn the volume knob slightly up and the pace knob slightly down.
For example, let's suppose we are both aiming to run at about 6:40/mile (ballpark).
It sounds like you are planning to do:
faster intervals at about 6:00/m
tempo runs and tempo intervals at (I'm guessing) about 6:20/m
fast continuous runs at about 6:40/m
easy runs at 7:45-8:15
average weekly volume about 60
I am planning to do something more like:
tempo runs / tempo intervals at about 6:25/mile
long intervals at about 6:40/mile
fast continuous runs at about 6:55/mile
easy runs... easy (frequently on trails)
average weekly volume about 70 (with somewhat higher volume in workouts as well)
(I'm also doing some very short speed stuff - strides, hill sprints, light fartlek-style stuff - which you may well be doing, but didn't happen to note.)
So, from my perspective, the paces that you propose look just a touch too fast (though I imagine that from your perspective, mine look a little slow). My thinking on this is informed by Canova's emphasis on paces between 95-105% of goal race pace (what he considers specific training), and specifically his approach of using long MP intervals and long fast runs at just a bit slower than marathon pace (building up from 90-95% or thereabouts). In my experience, the 95% approach makes it possible to do significantly more specific volume with significantly less strain.
A couple other thoughts:
I would think about running easy (really easy) on your off days instead of taking them off completely. Partly a matter of personal preference/what works for you, but I find that I recover better off a really easy run than I do off no running at all.
In general, I'm strongly in favor of just running easy days easy with no prescribed pace.