Hi,
Regarding the randomness of the 752 Hex Code, I consider it an almost dead-cert that it is not randomly generated, to the order of 10^(-200) (give or take a few orders of magnitude!).
I found how frequently each byte occured, and then found how many times did a byte only occur once, twice, etc. I then did the same with a randomly generated string of the same length. I then compared them (using a linear regression line) to find (approximately) what the relationship between number in a given category for random, and one for the code. In theory, if the hex code were random, this should be 1 (there should on average be the same number in each section). So, I repeated this test 10000 times, getting a mean of circa 0.976, and a standard deviation of 0.067. Assuming these values are normally distributed, and come from a distribution of mean 1, and the same standard deviation, this represents a sample mean z-score of -35, or not very likely at all.
If any statisticians can find errors in this argument, go ahead. And the code can be found here: https://pastebin.com/WWEbDcT8
Hopefully, this should give us the hope to go on.
I will have a look at the feasibility of this being a non-bijective substitution (i.e. A is converted to a variety of bytes, and likewise with B etc.) - see if the frequencies of a byte can be made suitably close to those that arise in english.
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