Yes, it is theoretically and mysteriously possible that God could call other Jews in the same way he called Saul.
Paul did not need any approval or blessing from the disciples.
Yes, he did. He had to be in fellowship with the one holy catholic apostolic church to be authentic. Otherwise it would have been like the Reformation or Mormonism. Since St. Paul is an authentic apostle, he was in fellowship with the authentic disciples that the Messiah actually trained, as opposed to those who departed from the faith or imagined they were his sheep.
1Then after an interval of fourteen years I went up again to Jerusalem with Barnabas, taking Titus along also. 2It was because of a revelation that I went up; and I submitted to them the gospel which I preach among the Gentiles, but I did so in private to those who were of reputation, for fear that I might be running, or had run, in vain. 3But not even Titus, who was with me, though he was a Greek, was compelled to be circumcised. 4But it was because of the false brethren secretly brought in, who had sneaked in to spy out our liberty which we have in Christ Jesus, in order to bring us into bondage. 5But we did not yield in subjection to them for even an hour, so that the truth of the gospel would remain with you. 6But from those who were of high reputation (what they were makes no difference to me; God shows no partiality)—well, those who were of reputation contributed nothing to me. 7But on the contrary, seeing that I had been entrusted with the gospel to the uncircumcised, just as Peter had been to the circumcised 8(for He who effectually worked for Peter in his apostleship to the circumcised effectually worked for me also to the Gentiles), 9and recognizing the grace that had been given to me, James and Cephas and John, who were reputed to be pillars, gave to me and Barnabas the right hand of fellowship, so that we might go to the Gentiles and they to the circumcised. 10They only asked us to remember the poor—the very thing I also was eager to do. Galatians 2:1-10
Yes, it is theoretically and mysteriously possible that God could call other Jews in the same way he called Saul.
God can only call Jews??
Catholic reasoning on display again.