I use a strip of electrical tape around the base of the blade and a strip around the part where the screw is. Both tapes disappear in the hilt so you won't see them. One or two wrappings should give you a nice tight fit into the hilt and then just screw it tight (not over tighten).
For the batterypack, this is my humble sollution:
https://www.youtube.com/watch?v=S4Mz4D-l7Nw&t=3sAnd if you look op General Malice on the forum, he and his wife created a lovely cradle for the batterypack.