And in the complete absence of any discussion in the Bible on it being God's plan to give every individual equal opportunity to make a choice whether to accept or reject Christ;
This is not true. It is your bias blinding you to the obvious.
John 1:12-13
But to all who did receive him, who believed in his name, he gave the right to become children of God, who were born, not of blood nor of the will of the flesh nor of the will of man, but of God.
John 7:17
If anyone's will is to do God's will, he will know whether the teaching is from God or whether I am speaking on my own authority.
Joshua 24:15
And if it is evil in your eyes to serve the Lord, choose this day whom you will serve, whether the gods your fathers served in the region beyond the River, or the gods of the Amorites in whose land you dwell. But as for me and my house, we will serve the Lord.”
Revelation 3:20
Behold, I stand at the door and knock. If anyone hears my voice and opens the door, I will come in to him and eat with him, and he with me.
Romans 10:9-10
Because, if you confess with your mouth that Jesus is Lord and believe in your heart that God raised him from the dead, you will be saved. For with the heart one believes and is justified, and with the mouth one confesses and is saved.
Mark 8:34
And calling the crowd to him with his disciples, he said to them, “If anyone would come after me, let him deny himself and take up his cross and follow me.
1 Timothy 2:4
Who desires all people to be saved and to come to the knowledge of the truth.
2 Peter 3:9
The Lord is not slow to fulfill his promise as some count slowness, but is patient toward you, not wishing that any should perish, but that all should reach repentance.
Deuteronomy 30:19
I call heaven and earth to witness against you today, that I have set before you life and death, blessing and curse. Therefore choose life, that you and your offspring may live,
Romans 6:23
For the wages of sin is death, but the free gift of God is eternal life in Christ Jesus our Lord.
2 Timothy 2:26
And they may come to their senses and escape from the snare of the devil, after being captured by him to do his will.
No, these are not proof texts; they are examples of texts appealing to people for a decision for Christ. This is where the tight circular reasoning of reformed theology kicks in.
"Well," the Reformed theologian intones, "the ones who chose not to continue in Christ and fell away were never really saved in the first place."
"How do you know that?"
"Because they fell away."