Jesus called me into ministry, although I do not personally have the gift of an apostle. I would hope that everyone who is in active ministry is called my Jesus into it instead of those who decided to become a minister as a career move.
I don't know how things work in your church, but in every Baptist church I have been a part of, the church
recognizes and
affirms those that the body believes have already been called by Jesus into ministry, and commissions them to go forth with support from that body.
Sure. But that's why we have a written word of God, to have a somewhat objective test and guide for our faith.
Some people think that granting that there is some possibility that the canon of scripture leaves one vulnerable to Mormons. I have found exactly the opposite. Mormon missionaries are quite used to dismantling belief in the closing of the canon of scripture. When I spent five months in conversation with Mormon missionaries, I granted them the possibility that the canon of scripture might still be open (they were surprised, but happy) until I asked them how one could know whether or not additional scripture was inspired. They jumped to the "burning in the bosom" testimony (which is fine if one wants to shut down their minds and be duped), so I showed them the differences between the teachings of the KJV (which they claim to believe) and the Book of Mormon, Pearl of Great Price, and Doctrine and Covenants. They claim the KJV Bible (and all other translations) have been corrupted, so when you press them to their logical conclusions about the KJV Bible being completely unreliable compared to the Book of Mormon, you simply make that point that their faith is exclusively on Joseph Smith, Jr.'s claims and the texts he created.
Once you get there (not that hard to do), you ask them about Joseph Smith, Jr.'s vision again, and they will give you one of the many versions of Smith's vision that claimed that 'no one was preaching the true gospel upon the earth' at the time of Smith's vision.
Then you simply go to
3 Nephi 28:7-12, 18-23 in the Book of Mormon and have them read Smith's pseudo-King James writing (cribbing from many different Bible stories) where it plainly teaches that the Three Nephites were commissioned by Christ to spread the true gospel in the Americas until the Second Coming, never tasting of death. In Mormon culture, they often talk about the Three Nephites and how members might have encountered one of them in everyday life (something like Christians believing they have "entertained angels unawares"), so they should understand this immediately:
Joseph Smith's vision AND the Book of Mormon cannot both be true.
Either Joseph Smith, Jr., received a lying vision claiming the gospel was not being preached (contradicting the alleged words of Christ in the Book of Mormon), or the Christ of the Book of Mormon is incorrect (throwing the value of the Book of Mormon away) claiming that the gospel would continue to be proclaimed in the Americas.
At that point, point them back to the King James Bible and explain the story of the Bible and the gospel (going beyond just the atonement) and tell them that the Jesus revealed in the KJV (which they claim to believe) is calling them to follow Him, no matter where it leads.
I have used this technique several times with Mormons and it causes a huge uproar. The first time I tried this line of reasoning, it was with two Mormon missionaries I had been dialoging with. One was so shaken he had an emergency transfer home, and I pray he came to faith in Jesus. His former partner was joined by a new missionary for the next visit, and the former partner essentially told me that he only had two months left on his mission and he was going to finish it (with the private implication to me that he didn't believe it anymore), while the replacement missionary looked on in shock. I was invited to the Stake President's home to have a conversation, and I talked with him at length about Mormon doctrine (with the two missionaries present) and discovered he was less informed about Mormon doctrine than I was. He got very upset by our discussion and I was asked to leave. The next day, the two missionaries stopped by my home to inform me that from that moment onward, they were forbidden to talk to me since they had been informed I was a "son of perdition" and would only harm their faith.
That basic pattern has repeated every time I have talked to Mormons about their faith. One has to be careful to lay the groundwork for trusting the Bible first, otherwise you will likely intellectually drive them into atheism.