As to "parkways", I always assume trailers are not allowed, unless I know specifically otherwise.
You are correct if a road is called a parkway do not travel it, not because of the hefty ticket you will receive but some parkways have low clearance for the overpasses.
I tow with a 04 Excursion V-10. I have 373 gears, but I believe there was an option for a different gear ratio that would push the tow limit to 11,000lbs. I suggest looking real hard at the gas excursions, they will be cheaper to buy and you will not need to bullet proof them.