It's not that essence of pot is clay. Pot is literally clay shaped into what we call pot and use it for various purposes. There is no pot as such. But, within the relative context, pot is a useful shortcut word.

Similarly, no matter how many worlds or realities you conceive, no matter how separate they may appear, they must share some common mechanism which allows the individual awareness to "travel between" them. Thus they share an underlying common layer, which, when you look at the universe at large, implies common ancestor.

Yes, the most obvious is that which knows. That is, you which you call I (the same way we all refer to ourselves as I). And I would perhaps add that I as such has no traits because traits are all observed by I/me.

Metaphors, since they must use relative concepts to get the point across, will always be misleading, but you can still view reality as water and universe as a river. Only the water is no substance at all, the apparent essence has no essence to speak of (the seemingness of essence is the same as that of the seemingness of pot). Moreover, that water is you, that is, I (which, furthermore, reveals existence as axiomatic).

And what's best, you can observe this unity even directly within the relative and as the relative -- consider oxygen on Earth. It's fused with your blood cells and simultaneously fused with cells of a nearby tree while it fills the space between the two of you.

Also bear in mind that when we talk about oxygen, we talk about handful of continuous quantum fields that interact and generate the behavior of oxygen (not some miniature balls floating in space). In other words, you cannot really say where the big cloud of Earthly oxygen starts or ends (within biosphere). And you can extrapolate from there to the end of all manifested phenomena/traits.

The point is exactly that while the painting has "very little to do with you" (or rather, it cannot change who you are), you are the painting (which again is sort of true even in relative, literal sense).