I like the composition on no.1
For the test shot- You definitely will get better results with your 600.
I would start with matrix and TTL-BL on the 600. Adjust the compensation + or - on the flash to adjust the fill. Matrix and TTL-Bl can give inconsistent results (meaning, can change a bit with even a small change in composition), so if you change composition or change camera from landscape to portrait (or vice versa), you may need to re-adjust your compensation. That's just someplace to start. If you can, shoot in RAW+Jpeg so you can make WB adjustments later. But depending on how much fill is being supplied I would try a WB of flash, cloudy, sunny, whatever it's like outside and check your results.
If your subject is in shade and/or you have a bright background, a place to start:
-Matrix Metering
-Manual mode
-Meter off the background, then stop down one stop using the scale in the viewfinder. The default setup is to turn the dial to the right. I would choose your aperture and go with it, so close one stop using shutter speed.
- For aperture, it depends on your lens and what you can do. Somewhere between wide open and two stops down. Open wider to blur the background, but stop down as needed for sharpness. The exif on your shot of the guy was f/22, if that's right, I would open it up a bit more.
-Set ISO to base ISO, increase if needed to get the shutter speed up if you need it.
-Set flash to TTL-BL (If you use TTL then start around -1.3 compensation)
-Add or subtract fill light on the flash using the back of your 600.
If the subject is in really dark shade, then the range of brightness between your subject in deep shade and background might be too much to balance the look - in which case scout another location or you will be dialing in more flash power and end up with a flashy look.
Just some ideas where to start, others may have additional or different ideas.
