Stacked Images in Mobile

Can anyone please help me. I'm pulling my hair out trying to deal with the issues that Fluid Engine/7.1 seem to have in regards to responsive design. I've designed my website, looks great on a computer, but if you are anywhere between a mobile portrait orientation and a tablet, it absolutely falls apart. To make matters worse, Squarespace customer service is either unwilling or incapable of answering any of these issues. All I'm trying to do is make the mobile experience EXACTLY as it was with Classic Editor where the images defaulted to a vertical stack, covering the full width of the screen, without cropping. That should be very easy but it's seemingly impossible with Fluid Editor between the ~425 px and 768 px. Even when I use plug-ins such as Squarekicker or Fluid Engine Tablet Spacing, the images then do what I want but the text doesn't follow (probably because it's not connected to the image as captions were in the Classic Editor). Below is a screenshot of what I'm talking about. About to leave Squarespace and start over somewhere else as this should be the simplest fix, but Squarespace seems to have made it impossible.

Here is the website if anyone has any ideas: https://www.bryanthomasphoto.com/work/commissions