You don't. Once the child is an adult, child support is moot and the ex is home free.
You can attach the estates of him and his parents
Yes, if a current case exist. If not, than no.
Your Social Security eligibility is not affected by your receipt of child support. One is for you; the other is for your child.
No, it is still owed with interest. The back child support was supposed to be paid while the child was growing up. Check your state laws.
The child can file prior to age 19.
yes dead beat.
extremely unlikely
No. The purpose of collecting back child support is to financially reimburse the custodial parent for the support he or she provided in the past. It is not intended to provide present or future support. The debt is owed entirely to the mother in this case, since she was the one who provided financial support to the child. There are cases in which an adult can receive the back child support owed to their parent, but these usually involve the death of that parent.
You still owe the back support. Once the child reaches the age of majority (as defined by the support order) there will be no continuing obligation.
Generally, no - although there might be an exception for a severely disabled child.
Child support that is awarded and not paid can be claimed by and adult child. A child support order usually expires when the child turns 18, but anything that is arrears can still be claimed by the child.
Most states do not allow a child to collect back support as an adult. Although the right to child support belongs to the child, support is payable to the custodial parent to assist in the care and upbringing of that child. If the custodial parent did not receive that support, then she (or he) made contributions that should have come from the other parent, and the right to collect the back support belongs to her.