Therefore, since "The soul that sinneth, it shall die" therefore, the only thing "permanent" about souls is whether they exist for eternity in heaven or go out of existence and "be as though they had not been".
Being separated from either the spirit or body is a state of death. Death is not the cessation of, but the absence or separation of one part of your life. The second death is the separation from God. Not non-existence. How can you experience separation if you do not exist to have that experience?
Now you have changed the dynamic. At first you stated the soul ceases to exist at physical death. I pointed out, no, the soul continues and the body returns to dust, unless humans preserve that body. The body you have now will cease to exist, not your soul.
Now you indicate a body and spirit, can exist, but the soul itself ceases to exist. You fail to see that people are physically cast into the LOF. Matthew 10:28
"And fear not them which kill the body, but are not able to kill the soul: but rather fear him which is able to destroy both soul and body in hell."
Jesus does not say the soul and body are killed. Jesus says they are destroyed, meaning that they do not cease to exist as you claim destroy means. If humans can kill the body, which causes it to cease to exist, but cannot kill the soul, how is removing the body via a human endeavor, cause the soul to cease to exist? Especially when Jesus said that cannot happen via a human.
You may say that God then causes the soul to cease to exist as an addition to human ability. But the same word is not used when God is doing the destruction. In fact you may say that then proves your point, because God only allows the body to cease to exist by human effort, and reserves Himself to cause both to cease to exist. That would be correct that God reserves that right, but does both happen in the grave? Not necessarily. A soul in sheol can exist, but the body cannot. A soul can cease to exist in sheol, but the verse does not say that it does, it just says only God can make that happen?. The point is not every human is killed by another human. Being killed is a natural part of life when the body itself can no longer sustain life. Jesus did not make the point humans cause all bodies to cease to exist, so why are you saying God causes that to happen, all the time? The point was to fear God, not humans. The point was not to say every soul and body ceases to exist at God's doing. Your point has been when the body ceases to exist, then so should the soul.
Scripture never places the soul in heaven without a physical body. That is only human assumption. The soul was in sheol, without a physical body (a body would not function within the earth), but you deny that Scriptural reference about Abraham's bosom given by Jesus, and declare, there is literally nothing going on in the grave, when the OT clearly pointed out the soul was in the grave, but had no knowledge of what was happening on the earth.
Hebrews 11 and 12 does point out the soul always existed while the physical body did not, because those in Paradise, post the Cross, do know what is going on, on the earth. Now that the soul was placed into a physical body, they are witnesses of the fact they were no longer dead, but made alive.
"Wherefore seeing we also are compassed about with so great a cloud of witnesses."
Those in the OT looked for and waited for that heavenly country and city, until the Cross, and the soul entered a physical body that was permanent to enjoy all Paradise had to offer. Now they are a witness to being made alive and can be a witness to what goes on, here on earth. Now a soul could immediately enter a permanent incorruptible physical body. That is why Paul wrote what he did. Not because he was comparing himself to the OT redeemed, still waiting in death.