You are going to have to leave your comfort zone on this one. Walnut is "brown", you have "pink" as a counter top. I would suggest going with another version of the colours already in the room. you have gray/beige and white. I would hesitate going white...but it can be done. You can move into the grays and be very happy (it would look very modern) or you can move into a beige that holds a hint of pink in it (not pink...but a blush of warmth). Or you could go really wonky and add in something like a brushed stainless steel look to the cabinets and have it go "space age". There are specs of blue/gray in this counter top. The next think to look at is an "ashwood" or dark gray wood presentation that has some blue in it. It would lighten the space yet still add drama that dark cabinetry offers.

the sink should be at 33" from the floor. your countertop height will depend on if you're using a top mounted or insert sink

normally the breakfast counter height varies from 36" to 42" if you want it to be perfect height select the stools for the counter first then check the height of the stool and add 12" to 15' in the height. distance between the stool seat and table top should be 12" to 15" max...

In that case , wall hung cabinet would be able to support the slab and sink. Is there a reason you want it it to be wall hung cabinet. You have made safe skirting space and even a floor mounted cabinet should be fine here. Regarding material, for the carcass you can opt for granite vertical slabs and BWP ply shutters for floor mounted one. But if you prefer a wall hung cabinet then a BWP ply carcass sould be good enough. The wall groove should be cut only on the longer side. Thanks, Nitin Cornerstone Designs, Bangalore