No offense, but I can't buy into your premise. Answers alone do not produce wisdom, for wisdom is understanding applied to action. Five is also an arbitrary number. Everything must be confirmed through experience, either externally in the world or internally through connection with the Ineffable.
Ebola!, those are some interesting questions. I'll try to answer them because I do feel like sorting out my thoughts in writing. I view things a bit differently from you...parallel your perspective with mine for what it's worth.
1. What is the relationship between quantity and quality? What is their ontology?
Quantity and quality are essentially the same thing and are contingent upon one another. That is, the more something is fundamental, the "better" (as to quality) it can be said to be and the more subtle it is, absolute fundamentality being the Ineffable, and absolute conventionality being non-existence. Conventionality is concrete, tangible, defined, local, individual, arbitrary, impermanent, and illusory. Fundamentality is abstract, subtle, undefined, non-local, universal, innate/natural/spontaneous, infinite, timeless, and real.
Quantity doesn't really exist. You have a bunch of apples, but in reality you have countless constituents forming various wholes we label as apples. So we have many apples, or a great many cells, or a huge number of atoms, etc. Quantity is relative to the context in which the question is posed.
2. How can the discrete coexist with the continuous? What is their relationship?
What is the continuous? From a fundamental perspective conventionality is impermanent and thus ever-changing, whereas from a conventional perspective it is the Ineffable that's ever-changing for it is perceived as the constant interplay between Yin and Yang.
Fundamentality and conventionality are not mutually exclusive and it is not an either/or matter, but a matter of degrees. Think of the Ineffable as the source and the universe as the emission, so to the extent that the Ineffable manifests as something concrete it is conventional. But all conventionality must contain at least some fundamentality to exist, for without contrast there is nothing (known only as the Nameless Tao).
Think of it this way: you can't examine a chair in isolation, you must consider its context. As the subtle empty space around it defines its physical delimitations, so must fundamentality be ever-present as a foundation within which conventionality may manifest.
What is the relationship? Well, a chain of causality regarding the physical realm can explain everything in it, but leaps of faith or discrepencies, depending on your point of view, will lie between the chains. To expand the chain and understand it more profoundly, bring the vertical axis into the equation, transforming the horizontal axis from something that comes full circle as a chain of causality into a spiral that connects with another chain one contextual level up. So pictorially you have a vertical axis with absolute fundamentality on top and absolute conventionality on the bottom, and a spiral around it like DNA.
As an aside, the physical chain of causality goes something like: universe, galaxies, planets, continents, countries, states/provinces, cities, districts, families, individuals, body parts, cells, atoms, the stuff of atoms, etc. I'm sure I've missed a lot.
The kicker is that absolute fundamentality and absolute conventionality are essentially the same thing, which is how the Yin and Yang that form the Tao merge into the Nameless Tao. This means the vertical axis comes full circle and is a chain of causality itself; understanding of the entire reletavistic spectrum constitutes an absolutely fundamental perspective, and to live fundamentally you understand relativity, so you don't question the contrast of things and you can live without constant preoccupation of thought.
Having said this, let me again address quantity and quality. Absolute fundamentality bears no distinction or definition, so everything is one and fragmentation constitues a drop down into conventionality. Think of absolute fundamentality as existence and absolute conventionality as non-existence. Absolute conventionality is zero, and absolute fundamentality is one. The Nameless Tao cannot be expressed in numbers because the very premise of a numeric field presumes a degree of innate fragmentation, in that the Whole is only one thing so there is nothing to count. Numbers come into play in consideration of the whole's constituents.
Since you say coexistence, how do they coexist in daily ever-progressing life? Well the present Now is all that exists physically. The past and the future are illusions. Linear time-bound understanding is how we perceive the timeless and non-local Ineffable, for to understand it all we'd see through physical existence and we'd be living in much higher planes.
I'm pretty tired now so I'll continue this another day. As you can see, my understanding contradicts some innate presumptions of your questions so it's difficult to give straight answers. Feel free to amend your questions into forms that might be more conducive to my type of explanation, and feel free to respond with your thoughts on these delicioius metaphysical ponderings.
At the very least I hope I've given you some questions from which you might push forward the fringes of your consciousness understanding.
