Re: How do moons maintain their orbit, given gravity and other forces

This is a great question. First of all, the moon is moving away from 
Earth at approximately a centimeter every year. This is affecting Earth's 
spin. By the moon slowly moving away from the Earth, Earth's rotation is 
being affected - the rotation of Earth is slowing down. The Earth's 
gravitational hold on the moon, is very strong. This attraction gives the 
Earth tides. That force, however is much weaker than it was when the 
Earth was first "born". The Earth's spin was much quicker, which presents 
scientist with the belief that the moon was much closer to the Earth than 
present day. Tides, at the beginning of the Earth's creation, were 
much stronger at those times.
Jupiter's four Galilean moons are also affected by one another's 
gravitational pull. The force of the moons and Jupiter is very great. 
This attraction is the cause, believed by many scientist, for two of the 
moons to have such large activity, Io and Europa. Io is a very volcanic 
moon, containing the largest volcano known in the galaxy, to date. Europa 
has a moving fluid of some sort moving underneath a layer of solid ice. 
These activities, volcanicism and moving fluid, are best explained by 
tidal heating - which is caused by the gravitational hold that Jupiter has 
on its moons.
To sum all of this up: Yes, the moons are able to slowly move out of 
orbit from their host planet - evidence revealed from early Earth to 
present day Earth. Yet, it is much easier to capture a satellite, than it 
is to release one. It takes a very long time!  The gravitational force is simply
much, much stronger than any of the effects you mention.

However if you still have further curiousity, please look into a these 
following websites:
 http://spacescience.nasa.gov/ http://astrobiology.arc.nasa.gov/
 http://www.space.com

I hope I have been of some help for you in better understanding you question.