Minks - my running form is much better as well when I run faster. Also, last year I started feeling really sluggish running my LSR's too slow (for me). I think training 5-6 days was wearing me out and I was struggling to run any runs fast even though before embarking on P&D I was already doing 18 milers at sub 8mm.
In the end, for the final 7 or 8 weeks I dropped the mileage and enjoyed it a bit more. I don't think speeding up a bit did me any harm. This summer I'm going to be fresh for my key sessions and the filling days can be very slow (maybe 9mm).
Therefore, my week may look like this:
Monday - rest
Tuesday - 9 miles with 5 at Tempo pace (7mm)
Wednesday - 6 miles recovery (9mm)
Thursday - intervals including 4 x 1 mile at 6:30mm
Friday - 6 mile recovery (9mm)
Saturday - rest or 5 miles recovery
Sunday - LSR - 16-18 with 6-10 @MP
Perhaps you could do something similar but without a couple of the recovery days,
What do you think?