Ok everyone, right now there around 6.5 million Americans unemployed and a good majority have been looking for 6+ months or more without any luck. So before you just tell the kid to go get a job realize that even McDonalds jobs are hard to come by in some towns, especially for someone who doesn't have job experience.
For those of you who tell him to "Move to a new town"... Little hard to do when you have no money to do it. Same goes for the moving out of his mothers house.
Before you all throw stones look through the otherside of the glass first.
Now to answer the original question:
Unfortunatley you can't change the fact that this is how your mother feels about the situation, and in her defense she shouldn't need to feel any differently about it. You are an adult now, its your turn to provide for yourself.
Considering your situation with the areas employment being 90% at the fort it won't be easy, but apply every where you can for any type of job (even if its picking up poo at the zoo) and hopefully one will bite.
In the mean time, you are obviously a bassist since your on the forums... Use your tallent! Take your bass and an amp and go to a park(keep the volume low) and play some nice bass solo pieces. Leave your guitar case open and hope for the best! Just make sure its not illegal to do that in whatever area you decide.
Hope that helps. Good luck!