Well; because of unbelief they were broken off, and thou standest by faith. ... And they also, if they abide not still in unbelief, shall be graffed in: for God is able to graff them in again. Rom 11:20, 23All is a big word, meaning all every last one of them. How can that be? I am pretty sure Judas is not going to be saved. I am pretty sure those pharisees that Jesus said their father is the devil are not going to be saved.
Paul is clearly saying that unbelief has broken them off but if their unbelief ceases God is able to graff them back in. Belief is the key. Yes actions are evidence of genuine belief.