sold pills to an under cover also had possesion of methadone, please i need info???

I live in van buren arkansas, I sold 12 methadone pills to an undercover cop about three weeks ago, i was caught on video in a parking lot doing this and he says he has the video.
He searched my truck and found 27 methadone pills i had in a bottle with my name in the script but the script was for hydrocodone.
He wants me to be an informant or go under cover to bust people I have bought and sold to/from, in order to just get Drug court he says.
He let me go tonite and even gave me my truck back when i gave him some info.
He informed me if i didnt do this for him he could impound my truck and sale it and i would go to prison for a very very long time..... what should I do???
This is my first offense, also what would the consiquences of the charges be if i did not do this for him and took the arrest and court date???
Please help me I have a wife and 1 year old child and have went down the wrong road, it took this to make me decide its time to change once and for all.What is the name of your state (only U.S. law)?

The police officer has no authority to create a deal for you.

Unless your attorney meets with the DA, anything promised doesn't hold a drop of water.