If you love it you should keep it. Off white or similar plain fabric sounds great. I would use the chairs as accent pieces in separate rooms and pair the couch with modern/mid century chairs that have clean lines and legs to give a sense of space underneath them. These could be a different accent colour or work back with the same tones as the couch depending on other pieces. You could stain the legs of these to work with the wood tones on your couch. Good luck would love to see the finished room.

I was left by my grandmother a lovely smallish hallstand. I used to climb in to the lower shelf and watch the adults when I was about 3 or 4 years old. I loved it! She had the old black bakelite phone on it in the hallway. It is shaped on both levels like a clover, so I always called it the Irish table. I painted it turquoise a while ago as the black varnish had become damaged over the years. It was made in the 1930's and was a wedding present to my Nanna. I repainted it white recently and I use it for holding a lamp, and a plant underneath.

I think you need a combo of chairs and a couch as the photos make it look like a through fare. black is very heavy so I would soften with a fur throw or similar. Focus on texture in your textiles and cushions. Mustard/ gold can look good against black. If you are changing soft I would go with something withe legs to lighten the look.

Go with your plan to feature colour Wall A and mount mirror on Wall A and place beachy art work on Wall B. My suggestion is to maybe consider using a paint colour for the featured wall that is tonally similar to paint on Wall B and not too dark so as to give room depth but not close it in with a dark heavy contrasting shade. Offsetting the hanging of the mirror closer (to the plant) could also add interest (and work with the shorter end of the sofa). Often going with you intuition is the best advice!!!