To move your text box lower on the screen, change the parameters to the grid call on line 194 to have a higher number for row. The grid lays the widgets out in a grid, and you can place things in different places by modifying these numbers. row goes down as it increases, column goes right as it increases.

To change the properties of a widget (in this case, your buttons), you store it in a variable. Here's an example: (I've cropped out tkinter setup)

def update_button():
  my_button.config(text="You clicked me!") #change button

my_button = Button(root, text="Click me!", command=update_button) #store in variable
my_button.pack()

You can call the config method on a widget and re-set any properties you'd like, such as command, background image, text, etc.