Rather than forgive you for your comments, I thank you for them. I welcome any constructive comments on anything I say.
I have not read the discussions you cited on string theory and I am no expert in the subject. I have read Brian Greene's "The Elegant Universe" which has given me about all I know about it. But here's what I think about your question.
Quantum Mechanics (and I suppose Quantum Electrodynamics too, although I don't really know) has proven itself to be the most accurate and comprehensive theory known to science. Moreover, from QM you can derive Maxwell's, Newton's, and (at least most of*) Einstein's equations. In my view, the currently known "Laws of Physics" are embodied by those theories. As far as I understand it, Dick has shown that those laws are unique to any consistent system.
My understanding of String Theory is that there are many potential candidates for hypotheses regarding how the strings behave and that it is extremely difficult to find the one among so many which, when solved, will produce the same well-known laws of physics. If they ever do find it, then presumably they will have found a more fundamental and comprehensive basic "Law" of physics. (It seems to me that Gauge Theory was up against the same sort of thing a few years ago, except that the number of candidate hypotheses wasn't nearly as large as it is for string theory.)
Now, whether they ever find the correct hypothesis or not, the question you raise is, couldn't it be possible for a universe to exist which behaves according to one of those other hypotheses? I think that Dick has shown that, no, that is not possible.
* I am aware that there is some kind of disagreement or inconsistency or other problem between QM and GR but I don't know much about it. That is why I included the weasel words, "at least most of" in my comment.