i see you have the confirm page set to store the sleected delivery city in a session variable named "eCartCheckoutForm_DeliveryCity", that's the first half, not in the eCart object, create a new shipping rule for each city, for example the shipping rule for Downtown Saint Paul would be configured as:
If Session Variable eCartCheckoutForm_DeliveryCity exists
Based on Session Variable Value:
If the session variable 'eCartCheckoutForm_DeliveryCity' is '=' a value of 'Downtown Saint Paul'
Subtotal for shipping cart is '<' a value of '100'
Charge flat rate;
other rules would be configured the same way just changing out what the session value is being compared to.