I use my monitor program for debugging that uses "Serial.print..." to write to the Monitor.
With ERW this does not work.
I'm no expert but my observation is that with the Leonardo the USB is in the processor itself and the USB link drops out and back in twice during every download. There are details on that elsewhere. You also need to wait for the instance of the serial port to established by adding.
while (!Serial) { ; // wait for serial port to connect. Needed for Leonardo only }
This I've done although I'm not convinced that works, nevertheless non-ERW environment works and ERW doesn't, shame because I really prefer your polished version and thought you should be aware. Without a Leonardo I guess your a bit stuffed. If I can do any tests to help you just shout up, in the meantime Ill use the tardy official IDE.
Thanks
Graham