If you are getting small droplets--they are prone to drift. I suggest use a nozzle with larger holes (like the green one) and reduce your pressure--until you get about 4 gallons per minute.
Walking 2 miles per hour with a 7 foot wide swath would give you 1232 sqft per minute.
Walking at 2.2 miles per hour with a seven foot swath would cover 1355 sqft per minute. At 4 gals per min you would apply 2.95 gallons per thousand sqft.
Naturally, you have to overlap your swaths slightly to assure full coverage of the edges. Nevertheless measure your swath center to center.