ok, simples things first:
to copy logic settings from one object to as much other objects you want, do this:
Select all objects you want the logic settings to be copied to. Then, hold shift and add the “master” object (that contains the logic bricks) to the selection. You can now copy the settings by pressing ctrl+c --> logic bricks
As for the rest, I need to think about it a bit
EDIT: ok, got it, it’s simple as well:
You just have to tweak your time ipo to go on with your animation.
What you did so far is this:
You animated the explosion let say from frame 1 to 100. Then you used the time ipo to tell blender to use frame 100 as your first real frame (by setting an ipo at y = 100 and x = 1). For ne next 99 real frames you reverse the initial animation by putting the next ipo point at y = 1 and x = 100.
So to go on with your animation, you will just have to set the next time ipo point to y = 101 and x = 101 and from there on extrapolate in a 45° graph to always have a 1:1 ratio of x:y.
As for the workflow: generally you animate your whole thing as you like and ignore the fact that the first explosion part is not the way you really want it. At this point you would have a normal time ipo of y=x. You alter that time ipo to just invert the frames you want and afterward you have to make sure that you set the time ipo back to y=x for the remaining frames.
Maybe my explanations are a bit confusing, tell me if there is still something unclear for you.
Looking forward to your final animation