I really like the route you've gone with the 1 gallon on the side, I've had a gigawort for a few months now and haven't tried it - I keep using my propane burner. This gives me some hope, I may give it a shot this weekend.
Have you had any issues with boiling over in the gigawort?
So this is probably a newb/dumb question. But if its going back into the kettle is it a must that your mixing pot is well sanitized? Not trying to be lazy, just want to make sure I understand.