A few numbers are off for my boat.
She motors easily at 7kts (currents notwithstanding), and would require only one refueling for this trip (might actually get away with no refueling at all, but running last day on essentially empty tank probably isn't a great idea). The diesel loves running at full speed (full speed is achieved at about 75-80% of max. rpm which, presumably, is where it should be)
70 mile days generally took me 10 hours of motoring a day. The only place where someone else might do better is in planning bridge crossings - I missed a few.
So, i am offering something like $10-$15/hr if we count this as an hourly rate, plus food and transportation.
Anyway, as much as I am sure people can critise this - I don't have too much choice here (other than letting my boat sit where she is for a long long time)