Hide custom Web Action in Work Item Editor Toolbar based on State [RTC 6.0.1]

 Hello Everyone,

I am trying to automate a custom web action to work item editor toolbar according to this Article:
https://jazz.net/library/article/782/#Contributing_the_Action

I have successfully deployed this custom web action plugin and the desired functionality is working as expected ie. i am able to create a linked defect from a user story.

Now i need to enhance this capability of this extension in the following ways:

1. Disable the web action based on state of the story work item.(I need this to be available only for few workitem states)
2. extract the data from the US work item and make it available in the defect work item(as a default value).
   I am not able to find the relevant API to extract the information (work item attribute data / State of the workitem).
   

On closer look into the the extension it is noticed that the current project area has been calculated by:

 this._currentPArea = new String(this.workingCopy.getValue({ path: "attributes.projectArea.id"}));

is there a way to extract custom attribute values with this type of extensions?

Thanks in Advance!
Abhishek Kumar