That sounds too slow, but based on most of what you said it sounds like it might work for you.
Here is my main problem with what you wrote: A 9-mile run is not an easy run or a recovery run for someone who is running 45 mpw or a 9-minute pace. It’s more like a long run.
Here’s what you should do: keep trying the slower easy runs for a while (maybe 8 weeks) and see what happens.
Can you run better workouts? If yes, then continue.
Can you increase overall mileage?
Do you race faster? I guess this is really the only one that matters.
If you get more fit, than that easy pace will increase naturally and you certainly won’t be at 9-minute easy pace for too long.
If you just plateau and stagnate, then the reason is probably that most of you miles are way too slow. Keep in mind that the reason you would do this experiment is so that you can run faster and harder on the 1-3 days a week that you do workouts.