Greetings in the precious Name of our Lord and Saviour, Jesus Christ.
Thank you very much for your letter.
Yes, I am the author of The Biblical Foundations of Calvinism article.
However, I think you are misunderstanding the doctrine of perseverance of the saints. We are not saying that people who have given their lives to the Lord will never fail or fall. The doctrine of perseverance of the saints asserts that true believers persevere to the end. Those who fall away without any repentance indicate that they are unregenerate.