I don't know how much coal you would / could carry with a trailer on the back of a F150. There quite a few long hills on 80 on the way back from PA = power going up & brakes going down. Whats your gearing, do you have a tranny cooler & brake controller ?
I've pulled I80 (Stroudsburg) through the Cross Bronx 3x this year - Pulling a fully loaded dual axle trailer through the Bronx is not a good place to start wondering about equipment. (produces rapid change in hair color) It's definitely going to cost you more than $50 in gas and tolls.
Don't take me wrong - I'm cheaper than the next guy - & I've run through quite few options & I've concluded no coal trips for me - your mileage may vary.
You can make up half your savings by increasing your coal storage capacity. When I called 'our guy' the price went down to $238 a ton w/ free delivery when I order 4 tons. I asked what their truck capacity was & I think they said 6 or 7 & that there is another price break for a full load. Plus they put it in the bin for you. Even better - If you have the room & access - contract a full semi trailer load. Food for thought.
Now if I had a diesel dump truck........wait, my wife would kill me - but then I would not need coal ......hmmmmm