The whole idea of hefting the propellant into orbit and then using it for a soft landing seems very compromising from an energy viewpoint.
As a fraction of the total fuel load its actually small. First stage fuel load is 418 tons, and landing fuel is around 32 tons, less than the reserve they carry to compensate for the additional burn time in case of a single engine failure out of the cluster of 9.
Empty weight of the first stage is only 18 tons!! Just the weight of the engines and effectively a tin tube with internal bracing - no wonder they crumple so easily.