You are trying to fix it from the wrong site
The reason why
include is in your opinion not working has nothing to do with
include but with the docs and the structure of the docs itself.
include is doing exactly what is is supposed to do in the training docs.
Nor DITA or other software will help you here ....
I will do a long write up on how to fix all that when I'll be back in Europe next week, so please stay calm and enjoy tea/coffee, there will be a bit work involved but it is not that bad .
BTW, you should attended my trainings, I had a long chapter were I explained all this