Now is a very good time of year to start pushing up the mileage. Back off on the intensity of the workouts whether it is 1, 2, or 3. Place your mental focus on building the volume. Do strides to maintain raw speed. Run any workouts at a "moderate" effort level so you can get in the volume without wearing down.
Distance running is mostly about your ability to maintain a high percentage of your speed for a long time and this is accomplished by building you Aerobic Engine.
To do this, spend about 6 weeks getting the volume up with low intensity. Like this:
45min (6mi)
75min (10mi)
45min
75min
45min
45min
90min (13mi)
=57mi
Maybe you start a little lower and move up to this, then move on to replace the 75 with 90min, the 90 with 100-120min. Once you do that, you can move up to 60min on some easy days. This will get you over 70mi/wk.
The other really important thing is to start pushing the pace on the 75min runs. Eventually you would be running up to 60min of it at a very high aerobic pace.
This will make you faster by virtue of being able to sustain a pace longer. Then you can do VO2Max and raw speed work to make you even faster.
Good luck