You pay the state where the original child support order was in place. Now if the custodial parent takes up legal residence in another state and opens a child support case there, the new state can help enforce and/or modify the original states order.
Generally, no.
Get a lawyer and have the matter taken before a judge. Even if the custodial parent refuses to respond to your attempts, she (or he) will have no choice in responding to a subpoena.
Generally yes. If the custodial parent moves away from the non-custodial parent, the custodial parent is ordered to make up the extra travel costs the non-custodial parent must now pay. The principle gives freedom to move, but discourages long-distance moves. In particular it discourages moves that are designed to deny access to the non-custodial parent.
In most states an 18 year old is no longer a minor and can live where they wish.
In some states, if the custodial parent moves more than 65 miles "as the crow flies" from the original address at the time of the custody agreement and does not get written permission to do so from the non-custodial parent, the court can (and sometimes will) remove the child and place him/her with the non-custodial parent. At that time the non-custodial parent will be given full custody of the child and even if the first parent moves back, they probably will not regain custody again.
Contempt of Court, which is consider a Change of Circumstances as regards a custody change. see link below
You still need to pay the child support. Hopefully the parent receiving the money is handing the money over. If the grandparents are having problems, they need to contact the courts to make sure they are receiving the money.
no
Yes, it does not matter where the child lives, you still have to pay it. The child does not stop being yours just because he/she lives in another state.
yes..
no see links below
No, but the new CP should immediately return to the venue that issued the order to get it terminated, or at least suspended until custody is worked out.Wrong. The newly-custodial parent will have to continue to pay child support until which time the "current" court order reflects that you no longer have to.Such things as a large pay differences could very-well continue having you pay child support but at a very small amount, in order to equalize the child's living conditions.(I thought it was BS too but I'm a single father who still pays child support)