Cryptanalysis

Hmm, there seem to be 2275 chars, which I find difficult to split into pairs - ?

Try this

http://www.math.cornell.edu/~mec/Summer2008/lundell/lecture1.html

the odd number was also my problem, but this is related to the transposition step (column swapping rectangle) and this rectangle needs to be padded so it can be you have padding chars
which make the sum odd...

Yes, the odd number of chars is due to padding. This is good info that makes restriction on possible key lengths.
I just want to add warning to anyone solving this. Make the key finding program by yourself. Do not trust any tool that you find online (talking about tools specific to adfgvx cipher). The implementation of key finding can be very simple, as the correct key stands out pretty well from the rest.