If you want to highlight the staircase wall then your could use earthy colours such as a yellow ochre! The wall could be enhanced even more by using suitable frames and making a good collage composition for all the photos that you have (I can see many lying on the dining table). This colour would match well with wooden furnitures

Definitely YES!

What soft furnishings do you have. You could pic out one or two colours as an accent colour and use that as your Base for the curtains. I currently have cream hessian walls and have a duck egg blue and chocolate curtains. I'm currently making matching Oxford cushion covers for the settees . If you can't find what your looking for ready made buy the fabric and have bespoke curtains made for you.

In civil engineering this condition is known as efflorescence this condition occurs due to capillary action of water in brick in which water contains diffrent salts comes on surface through voids of brick and evaporates and salt rest on surface as shown in image this salts may be harmful or not this depends on type and chemistry of salts generally it is not harmful