Ignore ALL the mess and imagine a wall on the right before the doorway into dining space. The wall will be built. The far end will have ~ 24” pantry closet. The proximal wall on right is where I’d put a light.

I think that a 2nd light fixture is a good idea. The height of the current one doesn't look too bad but if you're getting a new one, go with something taller which will appear to be higher on the wall.

They are clock outlets. You hang your clock on the hook and plug it into the outlet. They allow your clock to hang nice and flush to the wall. I’ve never seen the used for sconces. You can simply remove them and hang any sconce you choose on the electrical box these outlets are mounted on.

My daughter just bought her first home several months ago and she had a similar sconce that was cracked. I spent weeks on eBay looking for a replacement, and never found an exact match, so I settled for a replacement that was similar and had the right throat dimensions. I never saw anything on eBay that looked much like yours. You would have to look for two that were identical since you are unlikely to find the exact one in your photo so that would be much harder. There are lots of glass sconces on eBay, but I can't recall ever seeing someone offering a pair (although I occasionally saw a particular one from two different vendors). All of this is to say that your best bet may be to look at stores that carry new ones, like the ones other posters have provided links for.