FIFTH, going back to the 112, it is immediately followed by 111, my take on that, was that, if the decryption method includes a remainer/modulo of 26/25/27 etc., to get to the number of the alphabet letter, these two numbers will represent 2 letters, 1 after another, thus, think about such words with doubles instead of just any, soon is an example - o is the 15th and n the 14th, this also fits that 112 is before 111. The 102s will have a letter 4 letters away from it following. That is all of course, if the key does contain use of a modulo/remainer.
SIXTH, if the key does contain a modulo/remainer,it definetly won't be as straight forward as - divide by x and get its remainer, and since there will be other operations, keep in mind that it won't be only a plus / only a minus as that will mean that you will always get into -ve numbers (if it is a minus) and, unless it is just add 1, you will never be able to get just 1, thus never get the letter a (if it is a plus, excluding +1). Though, tbh, the more I get into it, the more I belive it will either not be including a remainer/modulo, or will just have quite a few other operations after it, in case it does?