It is calculated based on the needs of the child, the custodial parent's ability to provide for the child, income of both parents, custody agreements and other factors (such as which parent will be paying to maintain health insurance on the child). If you look online, you should be able to find a calculator for your state of residence that will give you a ballpark figure. All states have a formula established or court rules that determine the amount of child support to be paid.
Child support laws vary by state and you have not indicated what state you reside in. I suggest doing an online search with your state and see what regulations you can find.
That sounds too high - child support for two is around 25% of net income. Of course, there will be additional amount withheld for past-due support.
Not until your child is 18
No, that is still your child. Alimony would stop but not child support.
yes
no
yes
Generally, yes.
Doubtful. The child support is for the welfare of the child, not the mother. Check with your state child support office for specifics of the law in your state.
It depends on the state you live in and the age of the child.
That should have no effect.
No, as the payor has to approve the adoption
No. Child support is paid by absent parents.