Depending on the country, yes.
By filing for child support.
no, go to child support enforcement.
Filing a joint tax return should not increase or decrease a child support obligation.
yup
Make a request from child support enforcement for a new filing, but it will not be retroactive.
No. Child support is usually non-dischargeable.
Contact your State's child support agency about filing a lien.
no
No. Child support is not dischargeable in either federal or state bankruptcy.
Yes. Your State's child support agency should be able to help you with this.
Yes, that is still your child and you have a responsiblity to meet the needs of that child.
no