Although I am not familiar with plumbing, your remark about the repair advising a drill hole at the end of the crack reminded me of a repair that I planned for an acrylic fish tank. I am fairly certain that the drill hole is intended to relieve any stresses in the material, in order to prevent future propagation of the crack. Using epoxy may seal the existing crack, but it will not relieve any stresses that are already in the material.
So if the repair instructions say to drill a hole at the end of the crack, I would do so, even if it meant buying a new tool.
(In the case of my aquarium repair, The cracks were above where the water would be. I never did repair the aquarium, it is still in my basement