Paying child support does not automatically give someone the right to visitation. Assuming the other parent has custody and is not willing to voluntarily allow visitation, you'd have to petition for court-order visitation.
That depends on the laws in your jurisdiction. You need to consult with an attorney.
You file a modification. see link
Yes.
Yes, As I've seen news reports on father there being required to pay child support, but not getting to see their kids. Just like in the US.
If they are on SSI, than that's federal law. see link
Regardless of whether a parent pays support or not - the custody agreement determines who has rights. So if your child's father did not pay support but wants to see the child, and he has joint custody, he has every right, by law. This may not be morally right but it is legally right.
That dependent of state law, and you could even be ordered to pay more. see link
You will likely have to pay child support unless/until the child is adopted. see links
Yes, if he's over 18 and plans to see his child. If he doesn't, then he legally has NO rights to the child. Which is legal also... if he refuses to pay child support, then he gives up his legal right to see his child. End of story. You can't force someone to pay for something they don't want. But yes, if he's over 18, wants to see his child, then he must pay child support. Be firm.
Well not usually but it could happen
The NCP's spouse cannot be made to pay child support.
See link below