"On gravity someone, I can't remember who, ironically gave an explanation rooted in particles....oh dear. That is just what the theory of gravity lacks. The example was given of photons being associated with electromagnatism, I suppose that we might go on to associate gluons and bosons for the strong and weak nuclear forces. What, however, of the fourth fundamental force - gravity? What the heck, for example, is a graviton, has one ever been seen or measured? And why, for example, does our concept of gravity fall apart on the micro (quantum) and macro (black hole) levels?"
The description of forces as mediated via particles (including the graviton) is in essence just a mathematical trick. It is completely equivalent to describing them as quantized fields, but often an easier way to deal with them mathematically. The word particle in quantum theory is just a word to refer to a certain type of phenomenon. It's kind of a misnomer really because these force mediating "particles" (or any quantum particles for that matter) do not at all behave like particles as we intuitively understand them from our macroscopic perspective. They are also called waves in other contexts, which is equally inaccurate in the classical sense. The truth of the matter is that they have some characteristics of classical particles, some of classical waves, and some characteristics entirely different from either classical particles or waves. These words, particle and wave, in quantum theory are basically just a carry-over from previous, pre-quantum theory, understandings of how the micro world works (much like a car still has "horse power") and also for lack of a better word to describe a phenomenon so counterintuitive to our daily live experience.
So that's a graviton for you: a mathematical trick to describe quantized gravitational fields in an alternative but equivalent way.
In any case, per the above, each fundamental force is per definition associated with a particle, the graviton being the only one that is yet to be detected. Failure to detect them so far might very well be due to the extreme weakness of the gravitational force in comparison to the other fundamental forces, making gravitons undetectable by even the most advanced detector technology we currently have. It may equally well be due to quantum field theory not describing gravitation correctly. From our inability so far to 1) unify gravitation into one theory with the other three fundamental forces (which have already been unified into one theory) and 2) reconcile general relativity (the currently most plausible theory about gravity) with quantum theory, it is clear that there are things about gravity yet to be discovered. It is one of the exciting challenges of current day cutting edge physics.
"And why, for example, does our concept of gravity fall apart on the micro (quantum) and macro (black hole) levels? Why, for example, is the universe accelerating in its expansion?"
A Nobel prize for you if you can figure it out. The best current theories about the universe, although they fit very well with observations, have the universe consist mostly of dark energy and dark matter, phenomena in which the adjective dark basically just indicates the fact that no one really knows what the hell it is. They are basically just terms in an equation that are required to make the theory fit observation. The dark energy term is the one related to the accelerating expansion.
"The only answer you could come up with is that gravity equals the product of the masses divided by the square of the distance and then berate me for having the temerity to ask why! I am forced, therefore, to conclude that you are happy to be given easily digestible bite sized information to reassure you that science really has it all under control - is that really how you perceive the scientific method?"
I had no way of knowing your a-priori knowledge of the subject, so yeah, I tried to not make my answer overly complex. I didn't mean to berate you though. So my apologies if you interpreted it as such. Hopefully the above is more satisfying to you, even though obviously it doesn't answer all your questions as some of the answers are simply not know yet.
"Likewise on energy. You say it is nothing more or less than a quantity. Well, yes, anything that we might append a unit to is by definition a quantity, so what? Tell me why it is neither created or destroyed (while making the customary nod to Einstein). Or again are you happy with your "just is" explanation? I get it you will give me the circular elementary school ''capacity to do work'' explanation again, won't you?"
I don't know why it is neither created nor destroyed. Again, science doesn't aim to answer such why questions. All I can tell you is that an insane large amount of experiments of an extremely wide variety, executed over the course of several centuries have all consistently confirmed the hypothesis that it is neither created nor destroyed. So, the reasonable thing to do is to accept it as an experimental fact.
The why question is in anyway irrelevant. It does not help in to predict or explain anything nor tell you how to apply the knowledge. It's possible that we might find some underlying explanation to energy at some point, much like we discovered that thermal energy is actually kinetic energy of atoms. But that underlying explanation will necessarily again employ some other quantity to describe the phenomenon to which you can ask what is it and why does it exist. No matter how detailed and accurate our description of nature, you will always be able to ask the why question and it can never be satisfactorily answered. Fortunately though, again, it is an irrelevant question.