Have you added the 'Membership Fee' field to the webform under the memberships section?
Believe this will stop prices from being pulled from Civi.
Otherwise should pull across automatically as far as I am aware.
The MembershipPayment Added trigger should fire on the post hook, which might in some cases (notably the memberships and cases) mean the data is not complete yet (see this issue: https://lab.civicrm.org/extensions/civirules/issues/21).
I think the agileware version is now updated to use for eWAY Rapid API with the Responsive Shared Page method. This method does not ask for any CC details on civicrm and navigates user to eway site for the payment.
We did hit some problems using it on drupal webform, but I think it is already handled https://github.com/agileware/au.com.agileware....
It might well be that this turns out to be a situation that you can not solve with the current set of conditions. It is possible though to develop your own conditions (or have someone develop them for you).
Some conditions would be generic and could be part of the CiviRules extension as it will help other users too, others can be specific for a certain ...