When sending something, anything, to the my Arduino via the serial monitor I constantly get 2 more characters that I sent
You can change what the Serial Monitor appends, using the drop down in the lower right corner of the window.
one of them is \r. I can't find the other
Most likely, it \n.
This is what I use to read and show the number of received bytes:
There is never going to be a NULL in the input stream, when the stream comes from the serial monitor.