to the theme setting/custom style code but this is changing the image width. Is there a line of code I can add to this which will simply ignore the image? or any code that I can add would be helpful.
To be honest, there is no clean way to achieve this. Because your image is part of your content section. So it is really hard to keep the image wide but the content narrow. Remove the CSS that you added and replace it following. Following would only limit the max width of the paragraph in your blog to 900px.
#ArticleSection p{
max-width: 900px !important;
margin-left: auto !important;
margin-right: auto !important;
}