i would try this after user/pass and just change the intensity one by one until it gets better (from my experience the GCN cards will do best with a thread concurrency of 4x their shader number) might have to try 6144 if you get any in HW but this should work with your card, and you should be able to hit around 350kh/s
--intensity 13 --shaders 1024 --thread-concurrency 4096 -g 2 --lookup-gap 2 --worksize 256 --vectors 1