A high speed rejected takeoff is one of the worst places to find ones self. Based on the limited information available, which resulted in a runway overrun with most of the stopping distance already behind you, getting airborne with the load may well have been a better choice.
As you know, dumping retardant during a rejected takeoff means that often the brakes are coated with retardant, reducing brake friction to nearly zero, as well as creating a very slick surface for the aircraft. This is one reason that tanker pilots are strongly advised not to jettison during a rejected takeoff...plus the fact that as the weight leaves the aircraft, the effectiveness of the brakes is further reduced (the exact opposite reason of why ground spoilers are employed in some airplanes, or why we often raise flaps right after touchdown in tankers).
Doing nothing fast would have meant getting airborne, climbing clear of obstacles, jettisoning the load at that point over a safe area, and returning to land at your leisure. Rushing into a high speed rejected takeoff instead puts one in a very dangerous position.