Ok, for future reference for anyone else having these issues, here's how I've resolved these issues.

#1 tip is to follow Nicolai's instructions, but to add a minus sign in front of the make clean command. This will execute the command, but ignore the errors.

#2 is to ignore the multiple targets error from that point on.

#3 is that I assumed that Qt Creator would maintain the build-depends in the debian/control file using the .pro file. Nope. You have to do so yourself.

..and finally, the classic...remember to edit the on in the qtc_packaging directory, not the /debian directory. The debian directory is the output *sigh*.