Disagreement with the Calvinist Teaching

I finished a book by a Calvinist teacher. I don't agree w/ some of his doctrine but I understand why he believes as he does.
He feels salvation is from God , & man does nothing to earn it (true) ;therefore he feels once God saves (imputes salvation) someone they can never be unsaved.
He believes we are sealed and could lose our fellowship w/ God but never lose our salvation.
I disagree.
The Armenian doctrine teaches, that physical birth & spiritual birth are significantly different.
Although God doesn't give up on us ; we can turn our back on God even after being saved, and forfeit our salvation if we remain in a disobedient obstinate state.
Since God created us as free moral individuals, & because a person has to choose to become saved.
We do not choose our physical birth, but we do choose our spiritual birth.
Salvation comes only after conviction of sin & being called by the Holy Spirit.
I also believe a backslider (someone who turned away from God) does not become born again a second time but is reclaimed and begins again w/ God from where they left off & forsook God. That explains why some people can't get the emotional experience they seek when coming back to God's fellowship.
They are hoping to experience the same emotional assurance they had when they were born again.
What they must do is go back to where they left off & repent of their backslidding & sin and accept salvation again by faith.
God will restore and reclaim them. Often it must be done entirely on faith for a while without feelings.
I also struggle w/ the doctrine of predestination.
Calvinist's believe people are predestined to be lost or saved.
I believe according to scripture that the saved are predestined to be conformed to the image of Christ but not predestined to be lost or saved.
Since God is all-knowing (omniscient) he probably does know who will choose to become saved .
I must agree with the Calvinist when he says that God in His infinite wisdom chose a plan before the world began that somehow incorporated man's free will and His own sovereign will.
God did not force Judas to betray Jesus but He knew that Judas would.
Yet we should continue to pray for the salvation of our loved ones.
God put us here to intercede & pray so that our loved ones would change their mind, choose Christ, & be saved