G'Day Ian,
Rather than the 2x barlow, have you tried taking the lens out of the 2x barlow and screwing it directly into the nosepiece on the camera? This should allow you to come to focus without the full 2x magnification. It might help with sharpness of the detail.
The image looks like a good start!
I would hazard a guess that the proms are there, but you might need to over-expose the disc to capture them. To get a solar image with both proms and disc detail is usually the result of multiple exposures and stacking in my experience.
Al.