Congratulations on your first extension.
1 - That object was created precisely because you used .NET introspection and that is the class of the object being introspected. Another option would be to manually design the API and add the code directly to the extension project (without using a separate project and introspection) and you could create a cleaner API.
2 - I'm not sure why you can't access the return string. You might need to debug the extension by attaching the VS project to your IIS process.