Hello,
1) It’s because of the lumise plugin, it adds some content to our hover. We used custom CSS to hide it. Check now.
2) Theme Options > Header builder > edit socials element and add the new necessary socials http://prntscr.com/q2esph > publish your changes
3) Because you use Yellow pencil plugin and its single style tab. Use the global tab to apply styles for all the products https://gyazo.com/357daa3f1c6a483d94cbfd824cdc82dc in future.
We added correct code to child theme style.css instead of using yellow pencil custom.
4) It’s because of you custom code creayed by Yellow pencil. It used unsuitable in your case styles for that button. Check now.
Regards