My ex husband has not seen my 6 year old son since the day he was born. He is nothing but a glorified sperm donor at this point. He has paid about a years worth of child support at most during this time frame. I want to have his rights terminated so my husband (the person who has been there for Jacob since he was 2) can adopt him. Where should I start with this and how do I go about this? I am in Minnesota and he was in Ohio last they found him.

Get a lawyer, pursue the issue of adoption on the grounds of abandonment. They will probably have to publish notice in newspapers, and send mail to last known whereabouts of the biological father. They might be able to track something based on his social security number. Then if they can't find him you should be able to proceed, and if they do locate him, you might be able to have him sign off his rights so that there won't be any future child support against him.
If he has filed taxes, it would seem like they could locate him through the legal system, but that is only speculation. What I have told you is based on a friend of mine who went through a similar situation with their child and a dead beat dad.