How to Force text and image blocks to stack at 1150px wide breakpoint - Squarespace 7.1

Site URL: https://ruby-dinosaur-xmr3.squarespace.com/config/design

In Squarespace 7.1 ,  I would like my desktop website to switch to stacked content (mobile view) at approx 1100px wide instead of the default value. I've seen many examples in the forum that deals with the navigation bar only but in my case I want the whole site to switch to stacked view (images and text boxes). 

How can I do this ?  I've tried multiple CSS so far but none has worked. 

Thanks. 

password to the page : helloiro

have you solved this yet? If yes, can you provide solution for future members?

Not yet. Whatever bit of code I could find from the internet related to it doesn't work. I'm not sure how we can hack Squarespace default settings on this. 

Can you share link to page in screenshot? I think we can use some CSS to solve this.

You can try this link with pw helloiro

https://www.irodental.com/home

Hi. I see you solved. Do you still need help on this?

I issued a “offset” trick for the first picture but the problem remains at large. I haven’t found a way to force the conversion Before Squarespace default width.