You keep pointing to passages that say nothing about your salvation being guaranteed.
They absolutely do say that but I can’t force you to believe that or understand them.
If you’d rather try to work your way to heaven, thinking that there’s actually some good work to do that would please God and pay your sin debt, have at it.
But it’s not going to work out so well for you.
But then it’s not a gift, it’s wages due. And if it’s wages due, then it’s not grace, it’s what God owes you.
And besides, God doesn’t need our good works. He doesn’t need anything. All the good works we do for each other, God could miraculously do Himself.
Do you really want some?