There are two seeds of humanity, the Seed of Christ Gal. 3:16, 29, and the seed of the devil Mat. 13:38-39.
The Potter Rom. 9:21 made them according to His Perfect Will.
Dan. 4:35
And all the inhabitants of the earth are reputed as nothing: and he doeth according to his will in the army of heaven, and among the inhabitants of the earth: and none can stay his hand, or say unto him, What doest thou?
When the Bible refers to humans being "children" or "progeny" of a spiritual being it is talking about their character which includes the way they think and the pattern of their behavior.
44 You belong to your father, the devil, and you want to
carry out his desires. He was a
murderer from the beginning, refusing to uphold the truth, because
there is no truth in him. When he lies, he speaks his native language, because
he is a liar and the
father of lies (
John 8:44)
Jesus' enemies were "of their father the Devil" because they like he were enemies of the truth and, like the Devil himself they wanted to murder Jesus. The logical connection between them and Satan's nature was that the demons had been at work in their lives. This process is supported in the NT (e.g.,
Ephesians 2:2)
Instead of accepting this straight forward explanation Calvin refers to a "sovereign" work of God whereby the
heavenly Potter shapes them to become liars and murderers. The problem is, God is Holy, Righteous, Just, and loving. He would have no part in making anyone like Satan whose ways He abhors and who is in utter opposition to Him.
Now we come to what is a really staggering proposition - that making people who reflect the Satanic nature is God's
perfect will. I thought God's perfect will was that men repent of their sin and believe upon Jesus. I thought His perfect will was that we love Him with all our hearts and our neighbors as ourselves. However determinism did not originate in the Bible. The teaching was imported into Christian thinking from a system utterly foreign to Christianity.
Your interpretation does not work because it starts with the wrong premise. Paul was not talking about the salvation of individuals in Romans 9, he was telling the story of chosen people, specifically Israel and then the Gentile believers who were grafted in
Dan. 4:35
And all the inhabitants of the earth are reputed as nothing: and he doeth according to his will in the army of heaven, and among the inhabitants of the earth: and none can stay his hand, or say unto him, What doest thou?
This does not mean God is "free" to behave contrary to His good nature. That is not a matter of His power but His nature. God does not and would not fabricate evil. He might create something capable of being evil but all that is needed for that to happen is to give the creature a will.