You have asked to many questions in the single post. Secondly, if you are not clear about the Job Description(JD), then how anyone can tell you about the KRA or weights to the KRAs. First complete the job description, upload it here and then suggestions can be given.
By the way, after conducting training for the professionals from widely varied companies, I have started providing consulting services to institute Performance Management System (PMS) in the companies. To know more about instituting PMS in the company, you click here to refer my past post.
There is lot of misconception on the concept of KPI and KRA. To remove this misconception, I have uploaded my presentation on Youtube. To refer that video, you may click here.
I handle consulting on PMS. To know more about my services, you may click here.
Dinesh V Divekar
14th May 2014 From India, Bangalore