Not so fast. The unmerciful servant in Matthew 18:23-35 NASB had his free gift of forgiveness revoked.
Who said he had a free gift. If he received eternal life, and Matt 18 teaches that it was revoked, then why believe ANY part of the Bible? Are you comfortable with Scripture contradicting itself? Because God's gift of eternal life CANNOT be revoked, your understanding of Matt 18 is wrong. That should be obvious to you.
Jesus said this is how it is in the kingdom of God, and that his Father will treat each of us the same way the unmerciful servant got treated if we act like him. How does OSAS explain and interpret the passage so that the plain words of Jesus don't mean what they really mean?
First, there isn't anything there that teaches that this servant goes to hell. You just imagine that. You keep putting your non-OSAS bias into every verse that you can, when none of them teach what is CONTRADICTORY to Scripture.
In order to avoid obvious contradiction within Scripture, we must understand that being delivered "to the torturers" cannot mean eternal punishment in hell. But you seem quite comfortable with Scriptural contradiction. But the phrase is indicative of the severity of the divine discipline that falls on an unforgiving child of God in this life. See also 1 Cor 11:30-32 and Heb 12:5-11 for context of God's divine discipline towards His children.
The debt is remembered at another level - a level dealing with the Christian's practice, not his position in Christ. That's what you keep missing. iow, as long as a child of God is unforgiving towards others, they will experience God's displeasure in this life.
And are you just choosing to ignore that it is not the Israelites who did not believe, and who were cut out of the tree as a result, who will be grafted back into the tree, but a future generation of Israelites alive at the time of Christ's return?
It appears you are referring to Romans 11:17-24. The context is CLEARLY that Israelites had been "broken off" because of unbelief (v.20) and is contrasted with the Gentiles, to whom Paul was addressing, who "stand by faith" (v.20).
So your opinion of the passage is wrong from the start. The whole point of that passage is about being used by God, which requires faith. The Israelites, who lacked faith, were not being used by God, and thus, were "broken off". Why you or anyone else sees "loss of salvation" here is baffling.
Consider the time in which they lived, an agricultural economy. They were quite familiar with trees and dead branches. Such branches were of no use to the farmer, and were cut off. The same example is found in John 15 where Jesus spoke of throwing such branches into the fire. They were discarded, and described in agricultural terms.
What your view does is to spiritualize these examples. Everyone at that time understood the need to cut branches off a tree that weren't producing. Why? Because they were of no use to the farmer. Unless one has faith, they are of NO USE to God. That is the point; the whole point. Which you keep missing.
You read "loss of salvation" in passages that aren't even about salvation. In Rom 11, the issue is being of use to God, not getting or staying saved.
Now, I've explained clearly one of your so-called proof texts. You can either understand or continue to reject.