It’s not quite centered because of the padding added to the elements.
You would have to remove them for mobile. For example, the left padding on the phone icon should be removed for mobile:
@media (max-width: 768px) {
.top-bar-icon-1 {
padding-left: 0 !important;
}
.top-bar-icon-2 {
padding-right: 0 !important;
}
}