You will not be able to set these rules in the wizard, you need to edit the eCart object to add these shipping rules.
in the checkout wizard, select to include shipping, but leave the provider at NONE since you will be calculating your own shipping rather than using a lookup service.
open the eCart object panel (Insert -> WebAssist -> eCart -> eCart Object) Select your eCart abject and click the edit button.
on the shipping tab, you can defeine the shipping rules.
for the base rate rule, use the trigger:
Subtotal for the entire Cart Contents - is "<" a value of "50"
for the calculation use a flat rate of 8
the shipping country is stored in a session value named:
to charge different shipping rates to different countries, you can add conditions to the shipping rules using the based on session variable value trigger.