Theoretically, a fly sparge will be more efficient than batch sparging. However, in practice there are many issues which can keep fly sparging from being efficient, such as channeling of water, dead spaces that don't drain well, poor drainage design, etc.
Your water to grain ratio is fine. Since you are getting about half of your volume from the initial runnings, you have a good split to maximize your efficiency. Changing your initial infusion amount will not correct for a poor crush.
Low mash efficiency usually is a case of poor crush. Look through your grist and if you can pick out uncrushed kernels of grain in a small handful, then your crush is inefficient. Many LHBS will grind coarse because the last thing they want is for customers to come back complaining of stuck sparges. One way to check for your crush being too coarse is to extend the time of your mash. Take a small amount our to check the gravity at your normal time, then wait for a half hour and check it again. With a poor crush, you should see a significant jump in gravity readings over time. If the gravity readings are close to the same, then your issue is most likely channeling or poor drainage.