A flat rate shipping should be a flat rate amount, not the shipping value held in the cart.
Have you checked your cart to ensure that the items that should have free shipping have the proper value set for them?
What you have specified here should be working apply a flat rate shipping for the items. If you have any further trouble with this please post back with a copy of your WA_eCart folder.
As for the weight you can set it up in a similar fashion. You will check if the total weight < 30, if so then you will apply your flat rate shipping charge.
You do not need to worry about the inverse of these types of rules, if you are only crafting charge rules for the shipping then shipping will only be charged when it is triggered otherwise there will be no shipping charge.