Fireworks

It's New Year's Eve, and Bengt is setting up the fireworks. Usually he's not much for safety regulations, but this day he has all of a sudden decided to be really paranoid about safety. He wants to make absolutely sure no one can be hit by a rocket.
He knows that the rocket burns for a time t, and that it is supposed to reach a height h. But that's assuming that it moves straight upward.
While it burns, the acceleration has a constant size, and after that the rocket is only affected by gravity.
Naturally, Bengt would like to know how far the rocket might reach if it is fired at an angle.

1. Assuming that the rocket doesn't turn, and that there is no air friction, can we safely assume (for the purpose of these calculations) that the rocket has constant mass?
   
2. Come to think of it - assuming that there is no air friction, can we safely assume (for the purpose of these calculations) that the rocket doesn't turn?
   
3. Come to think of it - can we safely assume (for the purpose of these calculations) that there is no air friction? Remember we're trying to determine an upper bound for the distance, so we just want to know if there is any way the rocket could get a longer range due to air friction.
   
4. Assuming all those things, how far could the rocket reach?
   
5. Sture leeringly remarks that Bengt probably has no interest in safety, that he just wants to know how many of his neighbours' houses he could bomb. Naturally we trust Bengt, but if he was trying to reach as far as possible - would it help to attach several rockets to each other? If he uses a bunch of n rockets all attached to each other, how far will the bunch go?
   
6. What if he could change the time the rocket burns? Assume that the rocket gets the same amount of work done on it by the burning. How long should it ideally burn, in order to fly as far as possible?
   
7. And how far would that be?
   
8. If the rocket burns for b times longer, still with the same amount of work, how far will it go?