Hi
The best way to free the ball ends & bullets(the bigger ball ends) is to squeeze them with a pair of pliers while the metal ball is inserted in the plastic ball end.
Be carefull as the ball tends to shoot out at a fair rate of knots and could cause damage if it hits you in the eye(ouch). I slide a allen driver through the ball & hold the open end (the tip) with my fingers while squeezing the plastic with my other hand. Do this until the ball moves freely in the plastic.
The battery sliding around can be sorted in a number of ways : 1. I use a carbon fiber frame secured to the bottom of the frame with the battery posts so the battery has no option but to stay in the frame.
2.glue foam to the chassis to bracket the battery (on the main spine (under the main shaft) & on the other side as well). 3.make 2 U shaped brackets to fit over the battery from the top while ancored to the top battery brace.