You are going to need to put a ball valve somewhere on your return line. You have to be able to control the flow back to the tank. If your pump is too strong, the tank will overflow. If it's not strong enough, the sump will overflow. The ball valve lets you find that happy place in the middle where nothing is flooding.
You can put the ball valve straight in front of the return pump. But that creates back pressure (water pushing back on the pump), and some pumps are not meant to be operated with back pressure. Instead, you redirect the flow back to the sump. This puts a lot less back pressure on the pump, since you are simply making the water go in a different direction rather than stopping it cold.