Paul penned some are 'predestined ', now if you have a problem with Paul that is on you. Paul penned that 'some' were chosen 'before' the foundation of this world... (flesh age) that means at the casting down - overthrow of Lucifer. Isaiah and Ezekiel both describe Lucifer's rebellion and judgment, which took place before this flesh age... Lucifer is the only named entity that has been judged to eternal death. Genesis 1:2 describes the overthrow ... the earth became void and without form and flooded.
If so, my response would be, it was the plan of salvation that was predestined before the foundation of the world, not the individual (1’st Peter 19-20). Because each of us are born and created with free will. Unless I misunderstood your post?
Hebrews 2:14 Forasmuch then as the children are partakers of flesh and blood, he also himself likewise took part of the same; that through death he might destroy him that had the power of death, that is, the devil;
I don’t see where that supports individual predestination.
if your saying once saved always saved I have to disagree.
While I agree that no power may separate us from Christ, self can still denounce the saving Blood of ones salvation.