Fussy PNG on Wordpress

Hi! I'm saving graphic images for my portfolio website that are 991px by 667.96px with the "save for the web" function. When I see the preview on my screen on Preview (non-retina) the PNG looks great quality. However, once I upload to my website, the image displays in really low quality. The img becomes fuzzy, the colors distorted and is basically the opposite of crisp.

Some things to note:

I'm using a Wordpress theme

The image (AI art board) is exactly the size of the area is supposed to fill on the website (991px by 667px)

I even saved it at 200% (1982px by 1334px)

I used an img tag in the Wordpress text area as shown here:

img src="https://widemargincreative.com/wp-content/themes/plater/images/JJP_art2.png" alt="" width="991" height="667" class="aligncenter" />

I also noticed that my img was resized to a weird dimension of 960px by 646px

When I right click on the img and select inspect, I see this css attribute:

img[Attributes Style] {

1.    width: 960px;
2.    height: 646px;

Can anyone tell me why this is happening? Thank you so much!