Hello, @filmguerilla,
1..Sorry to say that, but you can only show the available icons in the theme for the social. Navigate to the Dashboard >> XSTORE >> Theme Option >> Social Share there you will see all the icons our theme has, just check the ones you want. Check the image: https://postimg.cc/TK95jkf2 The Instagram Icon is not available so you cannot add it.
2.. Actually, Yes you can do it. First, remove the CSS code that we share with you in the previous response and add the below code in order to solve your issue.
.single-product .product-share .menu-social-icons.icons-filled li a i{background:transparent !important; color:black !important; font-size:24px !important;}
Then save settings and check back to your site after clearing the browser cache. The result will be look like this: https://postimg.cc/5YfP7KFP
Regards 8Themes Team.