Hi John
I don't think it is argueing, mayber we are talking past one another. If the "balloon" inflated very quickly at the beginning, (inflation theory) space would appear flat(parallel lines would not meet) and our observable universe would be smaller than the whole universe itself. An ant siting on the surface of the balloon would see parallel lines are far as he could see. Truly, the fact that the balloon is increasing in its rate of expansion, that gives a flat geometry, as you pointed out, is correct. Using the balloon analogy does not mean I think the universal expansion is slowing down. I never said that. The balloon analogy remains a great picture to illustrate expansion. The point is, we are talking about the stretching of space itself, that is what we are talking about. That is the purpose of the analogy. Whether that stretching is slowing down, constant, speeding up (which appears to be the case) or variable, meaning early on it proceeded extremely quickly then slowed and now may be speeding up again (inflationary cosmology) is going to be debated for a whole long time.
I do not think man will get to the bottom of it. EVER. And yes, dark energy is only a theory, to try to explain the acceleration of this expansion...it is very mysterious, how this expansion is increasing! I love it, because it does show that no matter how deeply we probe into the well of knowledge, the well just keeps on getting deeper. This is clearly divine design, God intends man to struggle on and on in the area of trying to understand how God did it. Dark energy may be only a contrivance, or it may have a much deeper role, we do not know.
If we have any disagreement, it is only in your blanket pronouncements that people like Einstein are "wrong" I would say incomplete, but not necessarily "wrong". Evey piece of the puzzle does bring us evermore wonder and knowledge. The irony is, that what Einstein thought was his greatest blunder, the cosmological constant...we may be going back to that, in trying to get a model to fit all the observable facts. Einstein thought it was possible that the vacuum of space accelerated expansion but dismissed the idea. Now, that we know there is accelerating RATE of expansion, that the "balloon" is being filled ever more quickly, somehow, this amazing and overturning fact that is frankly as astonishing as the discovery of quantum laws 100 years ago...is going to make it more and more nebulous the HOWS and WHYS of the ultimate origin of everything. This is going to give some humility to man. Those that don't want to give God his proper place.
IMO, if Einstein was wrong, he was wrong about his attitude towards quantum mechanics "spooky actions at a distance" His words. He hated the fact that the quantum world seemed to have the paradoxes it actually does, but that is a whole different discussion.