I'm not even sure what your first question is asking.
In your pictures, don't go backwards. Just don't. It's bad programming practice and you want to break that habit now. In the second picture, if you want to communicate, just wire through and get rid of the control you have. The problem you're likely running into is you're doing that calculation and then need to send it into the loop. If that's the case, take a look at queues and the idea of a producer/consumer architecture. It's essentially set up for what you're trying to do.
For concatenation, go to the block diagram and hit ctrl+space. Type in "concatenate strings."
