I will do. Tomorrow, it is 11pm here. I am just reading the PhotoNotes article posted above. I'm guessing that the limited SS range setting on my 5D only applies when the flash is on, not all the time. It is in the Speedlite settings page. I will experiment. I certainly wouldn't want to neuter my available light Av settings.
I would use M mode but I find there are already too many settings to keep track of - see my 'needing a flash as all my photos have motion blur (because I set ISO to 100, not Auto)’ post at the beginning of this thread.
I think you also need to understand the fundamentals of an exposure.
You had motion blur because your shutter speed was too slow. Yes, raising the ISO will increase your shutter speed, but you NEED to be looking at all of your exposure data to understand why you are getting the results you are getting.
Aperture + shutter speed + ISO = exposure.
The great thing is you are using a digital camera- so you can look at the back of your screen and experiment!