Well, first of all, my congratulations for taking this work on. As I'm sure you've now realised, even simple product photography such as this involves a very different knowledge base and a very different set of skills from almost every other type of photography.
Your first example was frankly terrible, as you realised, because the lighting was hopelessly wrong, as SK66 correctly pointed out.
Your second link shows that you've taken that advice on board and I think that your latest version is now a bit better than the sample shot that you were asked to emulate - but that isn't saying much
As you've discovered, a polariser can be useful but has severe limitations. Correct placement of lights does everything that a polariser can do, and more, and I've never met a serious product photographer who uses one.
Correct. Some packing out is always necessary but it takes a bit of practice to get it right.
Dulling spray was very popular 50 years ago, fortunately we no longer try to suppress reflections, we now try to enhance and control them at the same time.
You've followed the advice, but not completely. Your overhead softbox needs to be MUCH closer, and only just out of shot. It also needs to be a bit behind the subject and pointing partly towards the camera. In lighting terms, your boot is very similar to the example subject that I used in my tutorial on creating specular highlights, here
https://www.lencarta.com/studio-lighting-blog/controlling-specular-reflections/#.VjzW6ysl-hE which, with all due modesty, is the definitive tutorial on the subject. You'll note that this involved just a single light, plus a reflector to kick 'spare' light into the areas at the front that were placed in shadow because of the position of the light, just like your boot. For the final image I did introduce a second light, gelled to colour part of the background, but that bit was just really playing, or showing off, and didn't affect the actual product lighting.
If you use the technique I outlined in that tutorial you'll also need to point some kind of light at the background, to avoid it going black (because little or no light is reaching it) because it's much easier to cut a subject out of a grey-ish background than a black one. Don't bring extra lights into play to make the background white, that will reduce image quality unless you have both a lot of experience and a lot of space.
So much for the lighting, but the pose is wrong too. If you look at sales pages for high end shoes you'll see that there is a set arrangement for the main image, as shown in this tutorial
https://www.lencarta.com/studio-lighting-blog/shooting-the-shoe/#.Vjx2WCsl-hE
You will of course also take shots from other angles, plus close-up shots, but the main image should always be taken at the angle shown.
Now what? My guess is that you've now finished this shoot to your own satisfaction but probably haven't supplied the images yet. My suggestion is that you experiment and take my advice on board, and supply your client with two separate sets of images - the ones that match the quality standard that they asked for and a set that show them that you can do far, far better - that's the way to improve your value to your client, gain more clients, make more money and improve your standards.