Child support question - NY

Hi. I live in NY and have custody of my child. I am also still married to my husband, but have been estranged for 3 years. My husband is court ordered to pay child support weekly, but has accumulated arrears for which I am taking him to court over next month. He has also filed a motion to:

1. Make me sign tax form 8332
2. Reduce/ eliminate arrears
3. Reduce weekly payments He has spent a total of 12 hours with our child since last year because the court has suspended his visits on 2 occasions and all other visits must be supervised.

When I filed for CS, the magistrate basically based the amount off of his unemployment combined with some actual earnings from a job he had. He is now saying he needs a reduction because his unemployment went down. He is an electrician and capable of making a significant amount of money when he does work, however, he is not actively looking for work. He is doing a lot of volunteering (which he thinks is work) but not making any significant attempt to find a job. I work and my income has probably increased by 1-2 thousand since we last filed, however, I work per diem and my salary isn't promised. I was wondering what I can do to ensure that his payments remain the same and the arrears don't go down. The arrears are basically from medical co-pays and medication for our child. He also has an account with his union where he can submit the receipts and get reimbursed. Should I bring that up? Should I ask for his wages to be imputed? Any advice would help. Thanks