Rpm 3600 is fine--ideal in my opinion. A Honda can handle it. Use high gear. With a little luck you should be covering around 11 square feet wide. Allow for a bit of overlap and you should cover about 5 feet out on both sides, 10 feet effective swath.
Not sure, I think your output should be about one-third of a gallon per thousand sqft, (about 43 ounces).
At 4 miles per hour,(352 feet per minute) if you cover a ten foot swath, you cover 3520 sqft per minute.
You need 151 ounces output per minute, (about 1.2 gallons per minute).
This will work fine. No need to soak the weeds with water. Lightly wet is fine. Let the chemistry do the work. If you are worried about the amount of solution...drive in low gear for the first few weeks (after adjusting to a suitable tank concentration).