First of all, make sure you first acknowledge the rules about posting on the forum:
http://www.saberforum.com/index.php?topic=117.0. All members are supposed to do this before they post anywhere else.
To answer your question, the LED's rattle in some sabers more than others. I certainly have a few that do this. Make sure the blade is resting against the LED--usually that stops or reduces the rattling. Insert your blade from above your saber and let gravity do its work, then tighten the blade using the retention screw.
For the battery pack moving, I've heard of a lot of different suggestions--inserting some pieces of adhesive tape to the inside wall of the saber to make the space smaller, using velcro to attach the battery pack to the inside of the saber, or putting something in between the pommel and the battery pack to cushion the battery pack. I personally put a bunch of rubber bands to cushion the battery pack. I've heard some using tissues to cushion the battery pack, but I don't trust that method as tissues and heat don't mix.
I'm sure others on the forum have suggestions, too. Good luck!