Here's one issue I can see with your statement about fusion creating the heaviest possible elements. There are Neutron stars. They're less dense than black holes and more dense than atomic matter.
What happens is that a star collapses to the point where gravity overcomes the electromagnetic force that keeps electrons orbiting around a nucleus. The electrons get crushed into the protons, forming more neutrons.
What you end up with is wall-to-wall neutrons, essentially a HUGE nucleus. Neutron stars are that dense. Visualize an atom the size of a football stadium. The nucleus will be smaller than a fly. Now visualize matter made up of nothing but nuclei packed in until they're in contact. Neutron stars are that freaking dense. They're way beyond your 'heaviest possible elements' scenario, and fusion has stopped, kind of by definition, when you hit a neutron star's density.
Then, when the neutrons collect in a sufficiently large mass, their gravitational force crushes the neutrons themselves, causing a black hole.
It's an interesting theory that could be explored. As I am only 16 I have not had too much time to think about these things, however I grow fascinated by the day. One thing in particular that fascinates me with the universe is that it is so complexing, that it is actually quite simple.
What you're thinking of is along the lines of the Big Crunch then a Big Bounce. I know you stated that a black hole could explode causing a big bang, and that's worth looking into, but essentially if the mass of the universe exceeds the gravtiational pull of the universe (or something along those lines) the universe will contract on itself until it reaches near a point of singularity. Then, the density and size would be incredibly small as Park Bierbower stated, "the size of one atom", and the forces that are contained are too great, causing another Big Bang.
Thus, it could be theorized that the universe is caught in an infinite loop of bounces, "banging" and "crunching" over and over again. Each bounce will have different norms. I was reading an article about parallel universes existing, and it basically stated that during the incredibly small amount of time after the big bang, if the first proton is made with different amounts of quarks/leptons, etc then the universe structure would be different, etc.
So essentially, we are the product of infinite chance, and the reason we see ourselves as perfect is because it's what we've accepted for so long.
from what I can gather, the universe (or more aptly the multiverse[s]) work like bubbles. If you imagine running water into soap, the bubbles grow and expand around each other. when they touch another bubble (which would reach to the theory saying universes are created when other verses/dimensions impact each other) a universe is created. we are more likely in an endless stream of "bubble" universes, and once ours expands past the point of its mass being able to contain itself, it will "burst."
~thats the idea I'm currently tossing around
as far as the actual question of "where does matter come from" the answer is more than likely not in reach, or if it is, there still isn't more than theoretical mathematics to describe it. The unfortunate thing is that the universe itself is considered a set, it is not a thing- therefore it is not subject to the natural laws that are contained within it, which essentially opens the doors to a myriad of possible explanations for the existence of matter. it also makes it difficult for us to come to a real conclusion, other than through deduction, which will essentially mean that we will need to understand many more things until we can even stumble on an idea that works outside of our natural state of logic.
Their question belies fundamental flaws in their argument. Firstly, where did God come from if everything has to be created? They have no answer. Secondly, just because we don't know yet, doesn't mean that there isn't an answer. In fact, it's what separates us from the 'faithful'. We are willing to be unsure until there is verifiable evidence. Thirdly, absence of an answer is not the proof of a different answer. This is a common fallacy called 'argumentum ex silentio'. No matter how you look at it, they have no valid argument.
For what it's worth (I am not a scientist), as there is not a single example of an actual beginning in the known universe (not a transition, evolution or conversion but an actual creation) then I assume, until proven otherwise, that the universe itself has always been here. The radiation and expansion that we measure could easily be the result of a 'perfect storm' with previous material exploding in a 'touch paper' fashion that had a knock-on effect, leading to the universe as we see it today. This is just conjecture but it does fit with what we see.
I hope this helps.
I think a better question would be:
Where did the underlying physics apparently in place before the big bang come from?
As mentioned in a previous post:
Hawking: "... the universe has the capacity to create itself from nothing over and over again... "
Physics has to have always existed.