Well you could figure out a decent estimate of volume flow per hour. By taking the line off the relief valve on the injection pump into a graduated container. Examine the fuel collected there at different amounts of time and engine speeds. In my mind that flow may in reality not change that much. At different RPMS or loads. Plus the amount of fuel actually burnt or used per hour is not hard to estimate. Close enough for all practical purposes. Just add the two together and it will give enough of an approximation.

It does not matter how often the pump is activated. Most of the time it will not actually be mechanically working. So that information is not needed. Even though it has the potential to act at half engine speed.

An example. The engine under road load conditions at 3000 rpm. Probably burns two gallons an hour. If the fuel supply system is in good condition. There will not be much change with fuel output from the return line feeding fuel back to the fuel tank. Measuring that amount coming out for five minutes at say 1500 rpm. Should produce a volume measurement that will be close enough. Multiply that by twelve and add the estimated actual fuel consumption per hour. You probably have a fuel flow through the filters of less than ten gallons per hour. After measuring the output return from the relief valve on the injection pump. You can get a pretty close estimate for all practical purposes.

I really try to keep things as simple as possible. Consistent with the requirements.

For a lot of reasons try to get a filter with a water drain feature.