have you tried deleting the Dreamweaver Cache file from the users configuration folder:
For the shipping charge, set the calcualtion to use:
Based on items with a specific value:
Total of 'Quantitity' where 'shipable' has a value of '1' 'time' '0.50 (-0.50)'
the (-0.50) will subtract the first shipping charge so that it only reflects the 22nd and above.