"The Tao is what exists as an undivided whole. People break it up into the 10,000 things..."

Through what agency? If, for example, I am undivided and whole, then who breaks me up into the people who further breaks me up into the 10,000 things?

God has Doubting Thomas, but we got Stompin' Tom.

To clarify:
What we quantify is neither brick nor wall nor Earth nor Moon. What we quantify is apparatus.

Huh? It's definitely a property of Earth that it weighs 3kg on a brick, say (because of its mass). And it's definitely a property of the Moon that it weighs 0.5kg on a brick, say (because of it's mass). The property of the brick is mass, the property of the Earth is mass, and the property of the Moon is mass. Weight is a property of our apparatus.

In the original post we used our magic scissors to part a semicircle from a whole circle, and later we used our magic sledgehammer to part a brick from a whole wall.

What is the whole, and what is the weight of this whole, from which we parted our weightless photon?

Heavy or light makes no difference.

Quantity is not a property of things, but things are a property of quantity. If there is no thing to quantify then there is no quantity. "Nothing" is no thing, so no quantity.

It doesn't matter if it's lightness or heaviness or weight or mass or whatever because each is a property which both brick and wall possess to a greater or lesser degree.

Weight is a property of brick, and more weight is a property of more brick.

Your reasoning seems backwards. The semicircle is as much a whole as is the circle, but consists of more parts. The circle consists of two parts; a line, and an equidistant point. The semicircle contains these same parts, and adds two end points which the circle lacks. Similarly, the circle is an essential part of any radius or diameter since without it they're just lines. I think your assertion that the semicircle is a part of the circle is false, and that the whole approach is weird.