Flex :: Application Interaction With Loaded Flash SWFs

I am creating a Flex application with a component that displays various dynamically loaded SWFs, one at a time (kind of like a kiosk). These loaded SWFs are created in Flash IDE, not Flex. They will not be created by us (we will provide a .fla template but that's it), so I am loading them into a separate SecurityDomain.

My Questions:

I want the application to be able to call methods inside the loaded SWF. To do this, would I just call Security.allowDomain("domain original app was loaded from") in the startup process for the loaded SWF? I want the loaded SWF to be able to throw events that are caught by the application. Can I accomplish this through the SWFLoader.swfBridge property? I am defining an interface for the methods inside the loaded SWF. But, I don't want to leave the implementation up to the customer. Instead, I want to provide another SWF that contains the interface implementation and have it be a constraint that the customer includes it in their SWF. I am not very familiar with the Flash authoring environment, how would it work so that the interface implementation SWF exposes its methods in such a way to be accessible to Flex? Is there a way to sign the SWF so that the Flex application knows that it is dealing with the original, not a spoof? How would the Flex code pass in arguments, since it is across SecurityDomain boundary -- is there marshalling involved (say if I want to pass in a Dictionary or some kind of object graph)? The Flex application may load hundreds of these smaller other SWFs during its lifetime. How do I make sure it doesn't keep using up more memory? I plan on using SWFLoader.unloadAndStop() and clearing all references in the Flex object that refers to it. Is this enough? Will the AppDomain for the loaded SWF be torn down automatically so that the class definitions are no longer in memory?