“How can you fall if you are without fault?”
You are confusing 2 different topics. The statement “Christ’s death has made us without fault” refers to a person’s eternal standing before God or salvation.
While we are eternally saved from our sins because of Christ’s atonement, we still need to be santified and set apart for service here on earth. Eternally, we are blameless, but on a temporal level there are still consequences we have to deal with for our sin.
All the other points you mentioned about remaining firm, remaining in His kindness, etc. demonstrate there are some who do not have a sincere faith. Many will claim to be followers of Jesus but will wither away for a variety of reasons. Those who have a true faith and have believed will never fall away.
You are just making this up. Show me the scripture that supports your made up belief.
The Scripture I cited shows just the opposite of your made up belief.
And remember, this was Paul talking. He himself had no assurance of his own salvation, but had to work out his salvation in fear and trembling. What do you think that meams?
Yes! Remember the parable of the sower. There are many “types” discussed there, but those who have a saving faith are not those who fall away.