For the gifts and the calling of God are irrevocable. Romans 11:29
Eternal, nor life, nor salvation are found in this verse.
You know well that this is no defense for your own views. Paul had previously defined both justification and eternal life as gifts of God: 3:24,5:151,6,17 and 6:23. So he didn't have to repeat himself in 11:29.
And no one has yet shown that Paul meant anything else in 11:29. He defined what he meant. We don't get to guess what he might have meant.
But, beyond that, Paul clearly taught eternal security in these verses:
Eph 1:13,14 - 13InHim, you also, after listening to the message of truth, the gospel of your salvation—having also believed, you were sealed in Him with the Holy Spirit of promise, 14who is given as a pledge of our inheritance, with a view to the redemption of God’s own possession, to the praise of His glory.
Eph 4:30 - Do not grieve the Holy Spirit of God, by whom you were sealed for the day of redemption.
2 Cor 1:22 - who also sealed us and gave us the Spirit in our hearts as a pledge.
2 Cor 5:5 - Now He who prepared us for this very purpose is God, who gave to us the Spirit as a pledge.
So, what has Paul taught here?
First, having believed, we are SEALED IN HIM (union with Christ) with the Holy Spirit of PROMISE, given as a PLEDGE FOR the day of redemption of God's own possession. This seal is a PLEDGE from God.
And consider this verse:
Heb 6:18 - so that by two unchangeable things in which
it is impossible for God to lie, we who have taken refuge would have strong encouragement to take hold of the hope set before us.
So, for one to accept your view of loss of salvation, 2 things are required:
1. Either prove by exegesis that Eph 1:13,14 4:30, 2 Cor 1:22 and 5:5 do NOT teach eternal security, or
2. Accept that God DOES break His promises and pledges, which makes Him a liar. Even though Scripture SAYS that it is impossible for God to lie.