OK, as I see things so far we've been working on the problem that you are having within your code and not your entire project. By working this way we've (I've) pretty much been ignoring the entirety of your program (sketch). The answers that I provided have ultimately led you to a dead-end solution where you will never get to your goal from here.
Using 7 different keypads with changing characters and matrices is that dead-end.
So let's do something different. Let's talk about your project. What are you trying to build? Just describe what a user is going to do when they walk up to your machine and what they expect to happen. And if you are OK with it then maybe I can help with code and explanations that are more in line with your expectations? We can talk about what hardware you are using and any other libraries that you may need and how they all can work together.
Best regards,
Mark