To have many products, you can do something like:
$productsPack = array("28", "29");
if(in_array(hikashop_getCID(),$productsPack)
echo JText::sprintf('PER_PACK_AT_LEAST_X_BOUGHT',$price->price_min_quantity);
else
echo JText::sprintf('PER_UNIT_AT_LEAST_X_BOUGHT',$price->price_min_quantity);
And add values in the array.
To change the text for "each", you can do the same thing but instead of the previous line to edit, the line is:
echo JText::_('PER_UNIT');
You should have something like:
$productsPack = array("28", "29");
if(in_array(hikashop_getCID(),$productsPack)
echo JText::_('PER_PACK');
else
echo JText::_('PER_UNIT');