I greatly enjoyed reading your essay. I think you are on exactly the right track. But, I have some suggestions that might be helpful.
You said, "In this essay I explain how existence, in terms of something from nothing, may be the consequence of a dimension of constructiveness. This requires a rethinking of the nature of fundamental dimensions."
I think you are exactly right and it is in that "rethinking" that I think I can help.
You began by making the tacit assumption that the "universe" is identical with the Big Bang and its consequences. I suggest that you enlarge your scope and consider the universe to be much bigger, and older, and that our visible "universe" that resulted from the BB is only a relatively small part of reality.
You said, "there is no special point from which the [BB-generated] universe originated." Using the familiar balloon-with-dots analogy to explain the anisotropy, this implies a large, extra spatial dimension in order for that balloon to exist. I would also point out in passing, that flatness vs curvature is different in kind from expansion vs contraction.
You are absolutely right when you say that "the universe is very, very large." But there is a huge gap between "very, very large" and being infinite. It seems more reasonable to expect that the size of reality lies somewhere in that huge gap. It seems likely that reality is very, very much larger than our 4D BB-generated space-time continuum, and yet not be infinite.
You said, "Nothingness as a cosmic origin has a certain appeal." Agreed. But even more appealing might be "ultimate simplicity". That would at least allow for some minimal starting point in case nothing really can come from nothing, and ultimate simplicity would be "neat and tidy" too.
You said, "An underlying complexity dimension may be the trigger for the emergence of a very simple substance capable of information processing." Considering complexity as a dimension may be an error. What I would suggest is that the extra dimension(s) is (are) ordinary spatial and temporal dimensions exactly like the ones in which we find our phenomenal existence.
And, here, I will offer my two most important suggestions for you: 1) Read Edwin Abbott's Flatland, or re-read it if you have already read it, and 2) look into the mathematical meaning of manifolds.
1) Abbott's small book is a delight and is easily available for free on the Internet. It is a quick easy read, well worth it simply for the critique of British society, which I think was its real purpose. But what you need to gain from it is an understanding of the psychological problem that people (I suspect this includes you, along with A. Square) have in accepting the possibility of the real existence of extra, large, inaccessible dimensions. You will also get a feeling for the mathematical concept of manifolds, although I don't think he ever uses that term.
2) The term 'manifold' has a very precise meaning in Differential Geometry, which is the study of calculus on manifolds, but I am not suggesting that you take a course in Differential Geometry (although it would be wonderful if you already have). The vernacular use of the term 'manifold' carries many of the important mathematical features, so there are many tangible examples of manifolds to make it easy for us to understand them. Here's the idea: A manifold is a special subspace that is embedded in a space of at least one higher dimension. A couple of characteristics make it special:
The manifold must be smooth and connected. Smooth means that if you zoom in on any point in the manifold, it gets flatter and flatter. Connected means that you could traverse from any point in the manifold to any other point in the manifold without leaving the manifold. So, for example, the inside surface of the intake manifold on your car is like that. A sheet of paper is a 2D manifold embedded in your 3D office.
The most important feature of manifolds for our purposes, is the fact that anything outside the manifold is, in principle, inaccessible to any structures or processes that are in the manifold. (You can't construct a plane figure on a sheet of paper that can reach into the room above the paper.) This is the real reason we can't see the extra dimensions, not because they are tightly curled up. It is what makes the extra dimensions inaccessible.
If we consider that our BB-generated 4D world is an embedded manifold in a 5D, or higher space-time continuum, there is an enormous expansion of the possibilities for structure and function. This would provide plenty of room for that "deeper constructive dimension in psychology" that you are trying to understand. It would also provide a place for that primordial, ultimately simple, origin of reality to take place, and it solves the problems of evolutionary psychology that you noted. Unfortunately, everything outside of our manifold is inaccessible to scientific experimental and observational apparatuses so it gets ruled out of consideration by Popper and most scientists.
You concluded your essay by saying, "I have argued that the universe could not have made a reality such as ours without a fundamental principal of constructiveness, and that this principle is best understood as a fundamental dimension comparable to space and time."
I think you are on the right track. I would suggest that you consider this new fundamental dimension to be exactly comparable to objective space and time: as additional spatial and temporal dimensions outside our 4D manifold.
In my essay, "A Proposal for an Expanded Paradigm", I have followed your lead but have gone ahead and done some speculating on how reality might have come to be in a higher-dimensional picture. I invite you to read it.