You do not have a lot of control over how paypal displays the item number and prod id, you cannot change the columns that are available, those are predetermined by PayPal. Same for the description, you will need to display this under the options category, you cannot separate this out, they do not have the display configured to show a separate description column.
as for the shipping, change:
<input type="hidden" name="handling_cart" id="handling_cart" value="<?php echo ($megan_isaacs->GetShipping() + $megan_isaacs->GetCharges()); ?>" />
to:
<input type="hidden" name="shipping" id="handling_cart" value="<?php echo ($megan_isaacs->GetShipping() + $megan_isaacs->GetCharges()); ?>" />
in order to pass the shi9pping as a shipping charge instead of handling.