Cooper tells Brand that the lander's linkages have been destroyed. So the only way they can slingshot themselves out of the Black hole's orbit is by manually controlling the engines. Without Amelia knowing, the others(Cooper, TARS and CASE) decide that TARS and Cooper would jettison themselves from the Endurance to shed weight and make the slingshot easier. Although it is given as a hint by TARS, Amelia had no idea that Cooper would also follow the same as TARS. It seems as if Cooper could have done it without sacrificing himself. But, he says so himself that the gravitational slingshot can be done only if the engines of the Lander 1 and Ranger 2 are controlled manually. It means that someone had to be physically present in both the crafts for the plan to work.
It might also seem that CASE could have gone instead of Cooper. But then there is another issue. Just seconds before detaching Ranger 2, Cooper confesses that he lied that there was enough resources for both of them, meaning only one of them could survive. CASE could assist Amelia in Plan B once they reached Edmund's planet. Since CASE is a robot, he won't have need for the resources. Cooper decided to sacrifice himself for Amelia as well as trying to find a way to save the people on Earth. At that point, Cooper did not have much hope of saving the people on Earth. He might have thought that after TARS collected the quantum data, they could devise a plan to send that data to Murph.
Anyway, everything goes well. But when TARS and Cooper launch themselves into the sky to find Brand, do they have any idea how they are going to? I mean, the 'beings' closed the tesseract so the might have closed the wormhole too. Even if that didn't happen, how can the craft in which TARS and Cooper set off supply them with the resources they need for the journey?