This sounds like a testimony of Moses’ judgment. You quote Rom 11:20 because of unbelief they were broken off.Rom 11:20 Well; because of unbelief they were broken off, and thou standest by faith. Be not highminded, but fear:
Rom 11:21 For if God spared not the natural branches, take heed lest he also spare not thee.
In Num 20:12 God told Moses “Because ye believed me not . . “ What was the consequence? Moses would not be allowed to take the congregation into the land given them.
Is there an even more drastic judgment to be taken against Moses? How about Moses: Deut 32:50-51 because ye sanctified me not in the midst of the children of Israel,go up and DIE in mount Nebo. Does this sound like being broken off, a sin unto death, or going to hell?
Surely this once dear child of God (Moses) cannot have grace applied even as the prodigal son of Luke 15:11-32: BREAK HIM OFF because of unbelief.
Jude 1:5 also verifies this: . . the Lord, having saved the people out of the land of Egypt, afterward destroyed them that believed not.