Would love some feedback.

It is a nice snap shot and with just two adjustments it could be much better.

1 The flash is too strong especially for direct bare bulb lighting. Yes, he is well exposed but he looks lit. Reduce the power a bit and this will look more natural, as he is obvioulsy in the shade of some trees.

2 The flash is too direct/hard. Bounce it off a reflector, above or to the side, or at the very least, diffuse it, so it has a more natural feel. Not forgetting to allow a bit of under exposure. I deally I would bounce the light from camera top right. This would create a nice softish light that would model him and not light the sole of his shoe, which is very bright, and that is not good as it draws the eye away from him.

Good composition, nice depth of field, nice expression and this is almost a very good portrait of a hansome little man.

Why did you choose to manually spot meter? I used to use a handheld meter, but it's rare today for me to be able to do a better job than my camera when it comes to measuring light.

Looks like you figured out the HSS setting, which helps, but spend some time playing with the compensation settings on your 580. I like to set the flash to fill around 1/3 to 1/2 of a stop under the ambient light. And use a modifier. Even the FStoppers disc would help in a shot like this.

Finally, practice on a subject (person) who won't distract you from examining the exposure and quality of light. Too often, we can't get over how cute our kid is, or how hot our wife/girlfriend is, and fail to really look at the image, rather than the person.

To much fill on the flash, what you need to do is balance the ambient light with the flash. The reason the flash is overpowering is because your camera is weighing heavy on aperture. Get out of automatic modes.