First of all, I don’t understand the benefit of adding the image to the database. Just add it as a Static image for the element’s background, and then append “?ignore_imgix” to the URL that appears in the Dynamic image field as described here. That will bypass Imgix processing.
A word of caution, however: You should make sure the image is optimized for the web before uploading it if you go this route. The whole point of Imgix is to handle website image optimizations “behind the scenes”, and since you’re bypassing that functionality, you’ll have to do it yourself, or page load performance might suffer.
FWIW, I looked at your page, and the image looks fine to me.