Featured image issue

I’m not sure if the issue described below is related to the recent update to the theme, as I just discovered the problem. When I created this page (and many others like it), I am certain that the theme did not perform this way.

Specifically, midway down the page I have inserted a small picture. That picture is now appearing directly below the navigation bar enlarged to full width. On mobile, it’s not too bad but on desktop the original picture is too low-res to be enlarged so much and it looks awful.

1) How can I suppress the enlarged photo from appearing on desktop screens, or at least prevent it from being excessively enlarged?

2) As an alternative, how can I prevent the picture from being “grabbed” from my page content and being plugged in below the nav bar?

The page I need help with: [log in to see the link]