Hello,
1. Please try to add this code in Custom css for mobile:
.vc_row-no-padding .wpb_column {
padding: 0 !important;
}
2. Could you please provide screenshot?
3. Unfortunately, I can’t recommend any 3rd party plugin.
Try to use default woocommerce elements or our [8THEME] Products element – http://prntscr.com/h8lkrc
4. Try to use Insert Footers and Headers plugin to add the code.
Regards