First: TBOM existed before Joseph Smith started a church, or established a priesthood of twelve apostles.
The Book of Mormon was the beginning of the process of the Restoration. It deos not mean that nothing else was to follow after it.
Second: Neither his church structure or priesthood are found in TBOM.
It is! The Nephites had a “church” established among them (following the ministry of Christ) which is mentioned in the Book of Mormon:
3 Nephi 26:
21 And they who were baptized in the name of Jesus were called the church of Christ.
3 Nephi 27:
3 And they said unto him: Lord, we will that thou wouldst tell us the name whereby we shall call this church; for there are disputations among the people concerning this matter.
7 Therefore, whatsoever ye shall do, ye shall do it in my name; therefore ye shall call the church in my name; and ye shall call upon the Father in my name that he will bless the church for my sake.
10 And if it so be that the church is built upon my gospel then will the Father show forth his own works in it.
4 Nephi 1:
1 And it came to pass that . . . the disciples of Jesus had formed a church of Christ in all the lands round about.
They also had false churches among them, as well as true ones:
4 Nephi 1:
26 And they began to be divided into classes; and they began to build up churches unto themselves to get gain, and began to deny the true church of Christ.
4 Nephi 1:
41 And they did still continue to build up churches unto themselves, and adorn them with all manner of precious things.
And at one time when they had all become very wicked, and lost the true church of Christ, God commanded them that if they would build His church among them once more, that they would be saved from destruction:
Mormon 3:
2 And it came to pass that the Lord did say unto me: Cry unto this people—Repent ye, and come unto me, and be ye baptized, and build up again my church, and ye shall be spared.
And their churches had both organizational structure as well as priesthood, which are mentioned in the Book of Mormon:
3 Nephi 18:
5 And when the multitude had eaten and were filled, he said unto the Disciples: Behold there shall one be
ordained among you, and to him will I give
power that he shall break bread and bless it and give it unto the people of my church, unto all those who shall believe and be baptized in my name.
Moroni 3:
1 The manner which the disciples, who were called the elders of the church, ordained priests and teachers
Moroni 4:
1 The manner of their elders and priests administering the flesh and blood of Christ unto the church; and they administered it according to the commandments of Christ; wherefore we know the manner to be true; and the elder or priest did minister it
2 And they did kneel down with the church, and pray to the Father in the name of Christ, saying
Moroni 6:
4 And after they had been received unto baptism, and were wrought upon and cleansed by the power of the Holy Ghost, they were numbered among the people of the church of Christ; and their names were taken, that they might be remembered and nourished by the good word of God, to keep them in the right way, to keep them continually watchful unto prayer, relying alone upon the merits of Christ, who was the author and the finisher of their faith.
Moroni 6:
9 And their meetings were conducted by the church after the manner of the workings of the Spirit, and by the power of the Holy Ghost; for as the power of the Holy Ghost led them whether to preach, or to exhort, or to pray, or to supplicate, or to sing, even so it was done.
(See further Moroni chapters 3, 4, and 6 for the role of the priesthood.) Furthermore, the Lord in the Book Mormon prophesies that in the last days when the Book of Mormon will come forth among the Gentiles, that He will establish His Church among them:
3 Nephi 21:
22 But if they * will repent and hearken unto my words, and harden not their hearts,
I will establish my church among them*.
So it looks like you got that awfully worng!
: There is not a single command by God for Joseph to start a church.
Commandment where? In the Doctrine and Covenants there are plenty. If you are referring to the Book of Mormon, there is not supposed to be, because the Book of Mormon was not addressed to Joseph Smith. But indirectly there is, as shown in 3 Nephi 21:22 quoted above.
: The “restitution of all things” verse does not apply to priesthood or to church. The law of Moses was fulfilled in Christ our Lord, he being the last high priest.
Those things which were preparatory to Christ will not return, i.e. high priest’s and priesthood. Thus, they are not found in the NT or BoM post Jesus.
All will return! The priesthood bestowed on Aaron and his discendents was eternal, and meant to last forever (Exodus 40:15; Numbers 25:13). They were not done away.
zerinus