monospace font & run script from external program

Hi, everyone.
I have two questions:

  1. How can I change font to monospace font? ok, if only for one widget.
    I show: button+some text+button, and I can make the same count of symbols in output, but they have different width because of different width of each letter, and widget change his size. Do you have any solutions?

  2. I make control buttons, and to see result at the moment, I run script (example: cat 1.txt) every second, but it seems not good, and how can I run this script on demand external?

Thanks, for you time.