So those who have faith are blinded? Unless you want to proceed with that contradiction, you still have a specific elect people (who have been blinded) who have not yet been "realized" in time. Whether that "all Israel" is all racial Israel or spiritual Israel, they have been elected. They have Jacob as their pattern...
I would reiterate Jesus' own "might be saved" statement. The Calvinistic view here may seem problematic, but I have to say that when I come across statements like this, I don't see a contradiction in Paul (even Jesus) having one desire but realizing on the other hand that it may or may not come to fruition (because of the Father's will...which I admit is not fully revealed) :
Thou hast neither part nor lot in this matter: for thy heart is not right in the sight of God.
Repent therefore of this thy wickedness, and pray God, if perhaps the thought of thine heart may be forgiven thee.
Acts 8:21-22
Follow peace with all men, and holiness, without which no man shall see the Lord:
Looking diligently lest any man fail of the grace of God; lest any root of bitterness springing up trouble you, and thereby many be defiled;
Lest there be any fornicator, or profane person, as Esau, who for one morsel of meat sold his birthright.
For ye know how that afterward, when he would have inherited the blessing, he was rejected: for he found no place of repentance, though he sought it carefully with tears.
Hebrews 12:14-17
And Jonathan said to the young man that bare his armour, Come, and let us go over unto the garrison of these uncircumcised: it may be that the Lord will work for us: for there is no restraint to the Lord to save by many or by few.
I Samuel 14:6
Or when David went before the Lord on behalf of his son - he spent seven days seeking his life from God. God let it be and allowed him to do so until finally, on the seventh day, the boy died (2 Samuel 12:15-23). God allowed the child to survive for that long and David continued to fast and pray while the child was alive. There was always that hope that the Lord would act - but no guarantee. Nathan had already prophesied the child's death (2 Samuel 12:14). Was David wrong to do this? Even when Nathan had prophesied what would happen? What about Hezekiah gaining 15 more years of life (Isaiah 38) and Isaiah saying he would die and not live? Hezekiah still petitioned God and (in spite of Isaiah's statement) was granted further life. Of course he died eventually, but even when something was declared, the man sought God. There is always an "it may be" with God. He doesn't tell us all His will - including the apostle to the Gentiles (or, it seems, Jesus while on earth as the Son of man - remember the Garden of Gethsemane...). Does that mean that all is predetermined? I think it means (if nothing else) that predestination is an explanation of truth found in scripture but that goes beyond our ability to properly and fully grasp. Paul, again, was not being disingenuous - but describing the deep desire he had on behalf of his people (after the flesh). Our desires and God's ways will not ever unite perfectly. But that doesn't mean our unfulfilled desires are necessarily wrong (or sinful).
I can only say that I see in the Calvinist theology, a biblical explanation for why things happen the way they do. But when it comes to walking out our faith, we don't walk out what we know based on what we believe God knows. We are responsible for the light we have - and the Reformed faith clearly places responsibility for the administration of predestination in the Lord's court.
Let a man so account of us, as of the ministers of Christ, and stewards of the mysteries of God.
Moreover it is required in stewards, that a man be found faithful.
But with me it is a very small thing that I should be judged of you, or of man's judgment: yea, I judge not mine own self.
For I know nothing by myself; yet am I not hereby justified: but he that judgeth me is the Lord.
Therefore judge nothing before the time, until the Lord come, who both will bring to light the hidden things of darkness, and will make manifest the counsels of the hearts: and then shall every man have praise of God.
I Corinthians 4:1-5
Paul was clearly not made steward of the full understanding of God's ways in predestination.
For myself, I can only say I don't want my dogmatism to overreach my faith. In other words, I am happy to say I don't really understand predestination but that I do see hints of its operation. Yet when I act in faith and obedience to God's Word, I do so only according to the understanding I have. I can say I believe predestination is true, but I really can't explain "how"....nor am I required to.