Just letting you know that a metal pressed splash back is only suitable if powder coated or left galvanized. It does not meet regulations when painted as the paint is not fire rated. Powder coating is. If you do it yourself, no one will know, but it is likely to dis-colour, blister or even singe! Powder coating does not make it easier to clean. But if you were really concerned about cleaning it you would avoid it all together. The recommendations above solve that easily. At the end of the day, a gloss finish will make spraying and wiping the grease, steam and fat away easily than a satin or Matt surface. Glossier the better, powder coat can control that.

Consider a glass mosaic tile in white. It will keep your all white but adds a touch of bling to liven the kitchen up. Some also have barely there colour in them if you don't want all white but don't actually want a specific colour. Sorry the photo attachment no longer works for me https://www.google.com.au/search?q=photos+of+white+glass+mosaic+tiles&espv=2&biw=1242&bih=585&tbm=isch&tbo=u&source=univ&sa=X&ved=0CCEQsARqFQoTCNjQgIvSucgCFYIrpgodw6cNVQ

Hey mate yes you need to decide the stone bench top finish height first , and at frame stage the window needs to be installed in such a way so that the bottom frame of the window is is set to that exact height. As you wont be able to move the window up or down at later stage.

You will have to remove to repair, and then it might break anyway. Re-asses once the mirror is off the wall, as to whether the glass can be re-silvered to form a complete mirror again, or whether the glass is too damaged.