Hello, @Kstb1979,
1&2- In order to solve your issue simply go to the Dashboard >> XStore >> Theme OPtions >> Theme Custom CSS >> Global and paste the below code at the bottom of the CSS box there.
.etheme-sticky-cart .etheme_custom_add_to_cart.button.single_add_to_cart_button.pointer{background:red !important; border-radius:20px !important;}
Note: In the above code the word “red” is the color you can change it with the color you want.
Then save settings and check back to your site after clearing the browser cache. The result will appear like this: https://postimg.cc/4m7tc1M0
3- No, there is no option in the theme to set the link of it. By default, it works like this and you cannot change it except through customization.
If you want paid Customization services submit a customization request to WPKraken team.
Regards 8Themes Team.