That's a lot of besides, and illustrates that Riker's "dilemma" in barge towing was not sufficiently well presented to the audience. It might make sense in certain circumstances, but the circumstances weren't explicated to us - or justified even if explicated.
However, if the speed at which the mission was to be completed was essential, Riker could not
disengage the tractor beam at any point. Doing so would mean he wouldn't be able to accelerate the barge until he again engaged, which would mean wasted minutes or hours. In the convoluted setup of the episode, the only way to minimize mission time would be to keep on accelerating until the barge was clear of the asteroids.