Emancipation

My question involves child support in the State of: Indiana

My stepson is 18, graduated from high school and does not plan on going
to college anytime in the near future. My husband is trying to get his support lowered due to being layed off from work. Is it possible to get the 18 yr. old emancipated if he's not going to school? There is one more son who is almost 17 and is still in school.
Any advice would be appreciated.
Also, we filed our taxes together for 2007. They want to see our tax return. How does this work when they should only be taking into account my husband's income, not mine?