Lovely design. With regards to the wood used. I agree that one of the timbers is black walnut. You mentioned one is ash. I believe it is oak from the open grain and medullary rays. I'm not sure what the light coloured timber is.
Fred
I'm glad you took the advice of @Adam W. to work on the back.
I also have a mirror finish using 8000 grit water stone for the back, and a micro bevel on the 8000 grit stone.
I believe it's worth the effort
Fred