So this discreteness, or quanta: what is it's origin?
Tong was clear to say that the fields are present in the Quantum vacuum, but fields are energy, not of a material nature.
So it appears to me that you are saying that discreteness emerges from the fields, but underneath the field level, are discrete quanta. Tong says there is no evidence of this underlying discreteness.
The field description and the particle descriptions are *entirely equivalent*. Neither one has priority over the other. It is another case of quantum dualism.