"2 / 8 = 0.29"

0.25 according to my calculations

pictures and /dev/random should give 0.5, not 0.57, if not they are not properly compressed and it's not a proper random generation, which I don't really believe. Maybe similar error as what happened with the 0.29?

The mean byte value in decimal should be 127.5.

I guess it may be something about the hexadecimal -> decimal -> binary conversion -> count instances of '0' and '1' in string in the python code that is doing something wrong (it's also inefficient to roundtrip through decimal when the original bytes are already binary in the computer and to involve strings in this at all). Does it remove leading zeros perhaps?