Terminate child support when child no longer resides with either parent

[SHANA]

I have an 18 year old son for whom i pay child support in the state of hawaii. His father and i have joint custody; with the father as the custodial parent. Sadly, my son is a drug user and was forced to leave his father's home when his step mother had him arrested for possesion in october of 2012. My son moved in with his paternal grandparents. The grandfather filed for emergency guardianship of my son and it was granted in december of 2012. I was living in kuwait at the time and was not notified my son was no longer living with his father and the grandfather made no attempt to contact me when he filed for emergency guardianship. It is unfortuante my son's temporary guardian is a drug user also and encourages my son's drug use.
In march (when my son turned 18) the child support enforcement agency sent a letter to the father in order to establish if the need for support still existed and to confirm my son was still attending high school. The father reported my son was still in school, but failed to report my son was no longer under his care.
My son graduated high school in may and i believe that due to his drug usage he will not be furthering his education.
I filed a motion and affidavit post decree relief requesting the termination of child support obligation and reimbursement of monies paid to the father from the time my son was no longer under his care.
What should i expect at the hearing? What do i need to do to prepare for the hearing? Are there other similar cases i can reference?

 

[army judge]

You're wasting your time. If dad didn't receive the support money, grandpa would have.
You can expect a wasted day. The kid's 18, graduated HGH school, he's stumbling, why not reach out to him? Ask him if he'd like to visit with you? Otherwise, the money's gone.