My child has to undergo a minor surgery and my ex is trying to be at the surgery because he has legal rights to be there. However, I have 100% physical custody and my ex has supervised visits through an organization. I can't get a straight answer from the Foc but he also hasn't used his visitation in over a year. can he be at this surgery?

Yes he can,
Why would you try to stop him? If he is not an immediate physical danger to the child, he would probably be a welcome sight. Why do you wish to deprive your child of the comfort he would bring?

Put your own bitterness aside and focus on what is right for your child. Hopefully this will be a wake up call and he will step up and be a father.