brown is another 'neutral' color that works with black and white scheme. Would be helpful if you can provide photos or links to the samples you have chosen.

These chairs are easy to recover and the range of fabric available today gives you plenty of choice. I say go for it. If you don't feel up to it yourself get an upholsterer, but plenty of YouTube tutorials about.

Once you go white (which I think is a great idea) you might find that the existing handles look good. If you want to change them I would suggest handles that are consistent with the period of the house/kitchen. And, I would keep them simple based on the design of the cabinetry. :-)

I was thinking maybe a pergola so that you can still enjoy the sun when necessary but have a small area where you can just relax with your family. What were you thinking?