Hello,

1) Please try adding the following Custom CSS in the Global Custom CSS area under Theme Settings >> Custom CSS.

a.button.product_type_variable.add_to_cart_button.add-to-cart-loop {
    border-radius: 10px;
}

2 & 3) Sorry but there is no option in Theme Settings available for that. It requires customizations and this is beyond our limitations and support policy.

Best Regards