In my years of experience as a mechanic, CV boot kits are ALL junk. They are very temporary fixes at best and replacing the whole half-shaft with even a reman unit from a parts store is a drastically better solution.
Max has it pretty much covered but don't forget about the E-clips on the inner side of the half-shaft splines. You'll need some muscle to get the half-shaft in and out but make sure the new one is in all the way before tightening things up and the E-clip isn't bent or broken.
Glad you found the problem so quickly