My point was that there was a penalty in this world for what he did.
God has demonstrated that he can kill the flesh of innocent people whilst they are still alive on the earth (Exodus 12:29), so there is no reason to suppose that he can't do the same to 'innocent' souls on the day of judgement. There is no reason to suppose that physical or spiritual death could not be inflicted by using the same rules which God has demonstrated in Exodus 12:29 - That innocent people can still be slain for his purpose regardless of their innocence.
Exodus 12:29 serves to illustrate the fact that "Eternal death in the lake of fire" would still operate according to the same rules as "God inflicting physical death of people who are still alive on the earth".
Unless of course, you can present some form of counter argument to refute this based on Scripture....
That does not mean the David lost his salvation or that his dead son was not accepted by God. David repented, believed by faith, God gave him grace, and forgave him.
Firstly, your assertion is based on God's new covenant with Christians which he promised in 1 John 1:9 - But this is not the Only promise that he made with Christians - Since, he also promised that he would have mercy on whom ever he wants, and compassion on whom ever he wants (Romans 9:15) - Basically, it means that God is still sovereign in regards to your salvation because your salvation does not depend on human will or exertion (Nor repentance), but it depends on God who has mercy (Romans 9:16).
Therefore, God can ignore what he allegedly promised in 1 John 1:9 since it is presumed that his counter promise is more important, and should therefore take priority over John - God can still do this without being called a "liar", since he is still bound by what he also pledged in Romans 9:15, 16.
There is no contradiction here, anymore so than "God contradicting himself" in regards to Ezekiel 18:20 - That the son will not suffer on account of his father's iniquity (Vice Versa) -
versus Exodus 20:5 and Numbers 14:18 - That God would still punish YOUR children on account of YOUR iniquity.
There is no contradiction if you understand that God can apply whichever rule he wants to suit his purpose - Since, either rule would be correct according to Scripture - Whichever rule is more important would depend entirely on the situation, but only God has the right to make that choice.
Secondly, David is a case in point, but YOU are not David and God doesn't have to forgive you as he forgave David - Since, the outcome of His judgment could've gone either way - Based on the premise that Romans 9:15, 16 can be more or less important than 1 John 1:9, which only God can decide.
That, God saw fit to forgive David and accept his child does not imply that he would do the same to everyone.