Hello,
First of all, mobile preview buttons are just previews, it does not mean that the options that you set when you are in the mobile preview that these options apply for the mobile only, nope. Options apply for the mobile if it has a desktop/mobile switcher like this one https://prnt.sc/GI7BEYKJSyD2
The computed box does not have this switcher, so, the settings you set there are applied for both desktop and mobile. In this case use not px units but vw for example. Also, I will pass the request to add that switcher for the mobile/desktop for the computed box of the single product.
The same for the WPBakery page builder. Go to Theme Options > General > enable WPBakery Responsive CSS Box-Module option to enable responsive settings for that module https://prnt.sc/JDo6o-oMftuQ
Provide us with WP Dashboard access to your site to check the AMP version issues.
Regards