First of all, I disregard any OT references. They were under a different salvation covenant that Christians are.
And most of your NT quotes have long ago been addressed by lady redfox, sojourner and anoia.
I will freely admit it now. I’ve been wrong about conditional salvation, as lady redfox calls it. We do have eternal security.
I think what clinched it for me was in thinking about “works” whether that be avoiding sin or living a good life. It took Christ’s sacrifice on the cross to get us salavation in the first place. If there were anything we as humans could have done to get salvation on our own, then Jesus didn’t need to die on the cross. If there’s nothing we could have done to get salvation on our own, there’s nothing we can do to maintain it or lose it — it is a gift from God. How can anybody claim to be as powerful as God to believe you can counter something he did for us?