Looks like you need to debug live via Serial1 now.
The 5 sec delay is not necessary for Mega which restarts when you open the IDE monitor, but some other boards (on my pc) don't like the monitor being open while programming and restart as soon as the upload finishes so I have a habit of putting this in so I can see I have not missed any of the startup msgs. I often swap sketches from board to board for testing.
No need to add the checks, if that is the case.
Yes that is correct.
RxBufferOverflow() only checks overflows for the sfStream 
so no use once you move to live testing.