So I suspect your fix extends the cycle time but why is the installer an idiot? How was he suppose to know the extend of your water infiltration problem? How deep is the pit? I think the fair solution is to pay him to increase the pit size, otherwise, I can see why he's reluctant to eat the cost. Did you try to understand what causes the problem in the first place? Is it possible to convert this system to a gravity feed system away from the home instead of pumping? You best have a back-up pump with that kind of water flow.