I don't have much time right now, so I will only address one of your comments and answer one of your questions, and I will get to the others some other day (Lord willing).
I definitely would not say that it has to be stretched. Instead, as I am about to demonstrate, it is a very rational deduction.
Jhn 8:51
Verily, verily, I say unto you, If a man keep my saying, he shall never see death.
Jhn 8:52
Then said the Jews unto him, Now we know that thou hast a devil. Abraham is dead, and the prophets; and thou sayest, If a man keep my saying, he shall never taste of death.
Jesus said that if a man keeps his sayings, then he shall never see death, and his hearers understood this to mean that he shall never taste of death. Elsewhere, Jesus plainly told his disciples that would die physically. For example, please consider what Jesus said to Peter.
Jhn 21:18
Verily, verily, I say unto thee, When thou wast young, thou girdedst thyself, and walkedst whither thou wouldest: but when thou shalt be old, thou shalt stretch forth thy hands, and another shall gird thee, and carry thee whither thou wouldest not.
Jhn 21:19
This spake he, signifying by what death he should glorify God. And when he had spoken this, he saith unto him, Follow me.
Seeing how Jesus said that those who keep his sayings would never see or taste of death, and seeing how Peter kept Jesus' sayings and died physically, the type of death that Jesus was speaking about must be what the Bible calls the second death (Rev. 2:11, 20:6, 20:14, 21:8). We know, from scripture, that he that hath part in the first resurrection, as Peter most certainly will, on such the second death hath no power (Rev. 20:6), and this perfectly aligns itself with Jesus' words in relation to those who keep his sayings never tasting of death. With these things in mind, we can very rationally conclude that when Jesus spoke of those who would taste of death when he returns, he was speaking about unbelievers who will taste of the second death at the end of his yet future Millennial Reign (Rev. 20:14).
Did David taste of death? No, he did not, and he never will. He died physically, but this is not what Jesus was referring to when he spoke of those who will taste of death when he returns. Hopefully, you can see the rationale in what I have just stated.
Jhn 8:51
Verily, verily, I say unto you, If a man keep my saying, he shall never see death.
Jhn 8:52
Then said the Jews unto him, Now we know that thou hast a devil. Abraham is dead, and the prophets; and thou sayest, If a man keep my saying, he shall never taste of death.
Jesus said that if a man keeps his sayings, then he shall never see death, and his hearers understood this to mean that he shall never taste of death. Elsewhere, Jesus plainly told his disciples that would die physically. For example, please consider what Jesus said to Peter.
Jhn 21:18
Verily, verily, I say unto thee, When thou wast young, thou girdedst thyself, and walkedst whither thou wouldest: but when thou shalt be old, thou shalt stretch forth thy hands, and another shall gird thee, and carry thee whither thou wouldest not.
Jhn 21:19
This spake he, signifying by what death he should glorify God. And when he had spoken this, he saith unto him, Follow me.
Seeing how Jesus said that those who keep his sayings would never see or taste of death, and seeing how Peter kept Jesus' sayings and died physically, the type of death that Jesus was speaking about must be what the Bible calls the second death (Rev. 2:11, 20:6, 20:14, 21:8). We know, from scripture, that he that hath part in the first resurrection, as Peter most certainly will, on such the second death hath no power (Rev. 20:6), and this perfectly aligns itself with Jesus' words in relation to those who keep his sayings never tasting of death. With these things in mind, we can very rationally conclude that when Jesus spoke of those who would taste of death when he returns, he was speaking about unbelievers who will taste of the second death at the end of his yet future Millennial Reign (Rev. 20:14).
Did David taste of death? No, he did not, and he never will. He died physically, but this is not what Jesus was referring to when he spoke of those who will taste of death when he returns. Hopefully, you can see the rationale in what I have just stated.