When my son was 4 I tried getting custody of him because I made the mistake of giving him up just so his father would have a family. I pointed out with no evidence to support his father's drug (pot) use during our marriage which lead us to the divorce. I finally figured out were very different people. Years later my son is a teen growing up with a dad who cares little about his kids education and emotional well being. My son is uncomfortable and is not open with his dad. When he has a problem he'll tell me instead. My son is failing classes and lacks the maturity of kids his age. The school and teachers there aren't helping either and though my son is a possible ADD kid, they never even questioned it. If I had my son when I asked for him, he would never have gotten like this.
A judge has immunity for judicial actions unless those actions are taken in the absence of all jurisdiction. This means if you sue a judge for a judicial decision, the suit will be dismissed. If you want advice respecting a change of custody, consult a lawyer licensed in New Hampshire who handles custody cases to help evaluate your circumstances and see whether grounds for a change of custody exists.
Not legal advice as I don't practice law in New Hampshire. I practice in Vermont ONLY.
No you can't sue a Judge. But you can get an attorney and fe for a change of custody