That's what I was going to say as well.
Quoting RiotPixie:Power of attorney
Power of Attorney, it basically gives another person the right to speak and act on your behalf (or as though they are you)... Standard PoA's are generally for real estate and finances, but you can have a PoA drafted for just about anything. I have DH's PoA and it only gives me the right to stand and speak for him in any type of courtroom (he has to be there too, but I can speak as though I am him [I'm more articulate and can express myself better]), it allows me to care for him and any minor child in his care (so I can take SS to the doctor or sign any legal paperwork regarding him if DH is unavailable, basically gives me the rights of a legal gaurdian), and I can talk to and deal with any type of government agency on his behalf (like child support, or the IRS for example). That is all the power our specific PoA grants me, but they can contain so much more.
I have medical power of attorney for my parents if anything happens to them at the same time. Just means I have the legal right to make medical decisions for them if they are incapacitated and can't do so for themselves.
When dh's father was in end-stage cancer, dh had financial power of attorney so he could make sure all bills were getting paid.
A power of attorney and child support are totally seperate issues, one does not have any impact on the other. Your husband would have to petition the courts to have child support changed or discontinued.