Is there any way to silence the output that occurs on TTY1 when switching runlevels?
I'm talking about the output like in the following image: 
I have a simple UI that may be running on TTY1 when the runlevel is changed and it corrupts the curses output, which looks very ugly.
Probably not: those messages are written to the console, and your TTY1 is just one of the virtual consoles that happen to be using it.
The service stop/start messages are not written by a child process of your command (otherwise you could redirect them to /dev/null).
On the other hand, you can suppress some other types of messages written to the console (kernel messages, as mentioned in How do I disable messages or logging from printing on the console/virtual terminals?).
But in a quick check of CentOS 7, neither redirecting the output of init nor using dmesg -n 1 affects messages sent going from runlevel 5 to 3. The command-shell does get logged out (which would be expected for your program as well).
