

I don’t think existence of the original matters unless you postulate the existence of something non-physical like a soul that can transfer over to the familiar copy if the original is destroyed, or split into two when both exist. Physically, a copy is a copy which might feel like “you”, but if the original is destroyed, the original “you” dies.
I don’t think biology is that simple, the body influences the mind (e.g. https://www.sciencealert.com/pooping-before-you-exercise-has-an-incredible-effect-on-performance) and isn’t just a vessel for it. But even if it was…
I don’t think putting a copy of your mind somewhere else will transfer your consciousness as well, so it’s not a suitable way to ensure your continued existence (unless you believe in an immaterial soul that’s independent of your physical body).
No, as mentioned before, it’s the continuity of physical existence, which I believe is crucial to the continued existence of “you”, otherwise even if a copy thinks it is “you”, the original is dead. Which is no use to me, even if a simulacrum continues to exist it would be only for the benefit(?) of others.