David said he would be with his dead child after he died, but it never said at what location.
The story of Lazarus and the Rich Man seems to give a description that those under God’s grace went to a mostly pleasant place (which some call Abram’s Bosom or some call Paradise). This place seems to be far from the perfect heaven since you are in the midst of those who are suffering in their punishment.
Romans 7:9 says “For I was alive without the law once: but when the commandment came, sin revived, and I died.”
I have no idea how you can get “age of accountability”. If there is “age of accountability” then is there “intelligence of accountability?” “Time Era of accountability?” “Geographic residence of accountability? “
David was fasting for the sick baby to the point that his servants were worried that he might be suicidal.
When he is finally told of the baby's death, he stops the fast and speaks, with obvious relief, of eventually joining him.
The "unnamed location" could not have been the "bad place" if David had this positive attitude about joining the baby.
Paul speaks cryptically, but not unintelligibly.
“I (Paul) was (past tense) without the law (before he learned the law)...
when the commandment came (learned the law, became accountable)...”