You will need to personally visit the courthouse and fill out the necessary forms. Your signature must be notarized (the court clerks can do this) and the papers filed with the court. A court date will be set and the judge/magistrate will hear your plea, where you will need to present solid evidence for your reasons why child support payments should be terminated.
Yes, the court will terminate child support.
Termination of parental rights does not terminate one's child support obligation.
by paying it until it's paid off.
because the custodial parent passed away,
The only way that parental rights will be terminated is if both parents and the family court agree that it is in the best interest of the child to terminate them. Simply wishing to stop being responsible for child support typically is not sufficient reason to terminate because it leaves the child in the position of not being cared for financially. Adoptive parents become natural parents with all the rights and responsibilities that entails the moment the adoption papers are finalized.
I suggest you consult with the other parent and an attorney on this. However, keep in mind that terminating parental rights does not terminate one's support obligation.
Make an official request with child support enforcement. see links
Age 19.
You can't terminate your obligation to support your child. That type of order must be decided by a court and only when the child is being legally adopted such that another parent will be responsible for the support of the child.
I'm not familiar with Canadian law, but moving the child out of state in the US would not terminate support.
Termination of parental rights does not, in itself, terminate child support.
Yes, until/unless the child is adopted. see links