[Sticw]

This eternal life gift is integral to the faith as the Lord's Prayer is all about Jesus died on the cross for our sins so we can have eternal life. If we believe in this, we are a Christian

So if we accept that Jesus died on the cross for our sins but reject this unexplained unknown unproven notion of eternal life, even though it is a gift, we are not a Christian, right?

As long as you confessed your sins and accepted his Grace you are forgiven and in exchanged you are seen as part of Jesus and goes back to God.

Maybe when your time is up you can talk to God about eternity. 

Jesus said that when he returns in his second coming he will judge and he will reject many who calls upon him as he know not of them. I believe what he said was that you can accept grace but you must take up your cross and walk like he did his ways. There will still be judgement. It is not a free pass to sin willfully. And he said eternity for life on this earth is not the final destination. You are in this world but not of this world. Perhaps there are still many things to be done beyond this current reality. Even the observable universe is only a fraction of reality or illusion. And God is beyond this space and time and so will his kingdom be beyond our comprehension.

Safe to say you can stop thinking about this eternal life but focus on your relationship with God.

Beyond this I have no further answers for you my friend.