Font-size bug from 89 characters in paragraph

[Anthony_E_B]

Hello everyone. 

(Sorry for my bad english, I'm french)
So I have an HTML page with a header, a footer, a lateral menu and of course, content.
It is perfectly sized for desktops and mobiles (thanks to a media query I invented, which is :

@media screen and (max-aspect-ratio: 7/8) and (min-height: 1100px){ /* MY CODE HERE */ }

 
The content is perfectly adjusted like this :

, thanks to: html{font-size: 200%} in this media query. 
I precise that  ALL my font-sizes and padding between divs / paragraphs are in "rem" unit.  
But the problem is, that when I exceeds the precise nuber of 89 characters, the texte suddenly look like this : 

But only on mobile devices (with the media query I said previously)... 
I visualized this with the Chrome developer tool -> Device toolbar (Ctrl + Shift + I  then  Ctrl + Shift + M) 

There I do a little as if it was not serious but it's days that I drudge everywhere and nobody was able to give me an answer ...

I put the page online so you can watch it more precisely...
http://vincentvincent.rf.gd/l-histoire.html 

Thanks for your help.