They say the width should be half the size of the table width. Height is not an issue.

What is the height the fixture will hang from? Is the ceiling angled to the center at 14-15' or to the kitchen at 14-15 feet so that they spot it hangs from may be no more than 12 feet? That makes a big difference. Yes, some large fixture at or near the width of the table are being shown, but do notice that they are hung higher over the table to compensate for headroom when standing at the table, sitting or standing (when many people will lean in a bit), much less setting the table, serving or placing things on the table. The most common DR table height is about 60" or 5 feet, maybe a few inches higher. That puts the bottom of the fixture at or near eye level for most folks. With a taller ceiling and a larger fixture, you may want to raise that by a foot, give or take depending on the fixture and ceiling height. If you go to 6 feet and te fixture is 5 feet, it will make a huge diffference whether it hands from 12 feet or 15 feet (one foot of chain or 4 feet of chain). I would probably stick to the single level, and if this is a spot that is still being built, I wouldn't buy the fixture until the walls and ceiling are in place and you can be sure of heights, widths, etc.

Put in the one you want to clean grody muck off of on a regular basis. As in every 2 weeks. And plan on how you’re going to reach it to remove each of those crystals to wipe them down individually. An articulating ladder rather than climbing on your island would be the better idea. But its a lot more work.

I would consider sculpture or something with organic lines, rather than rectangles. Sometimes you can find small or lightweight pieces with solid backs that you can hang with 3m command picture hanging strips. I do like the idea of candle sconces. I am a big fan of wall vases too. Maybe look for driftwood pieces? Resin starfish are easy to decorate with. Or lightweight pottery wall art. (I have a gorgeous pottery fish that I am trying to find a place for.) Shallow live edge floating shelves with objects leaning against the wall could be interesting. If you are interested in sculpture, look at Arhaus, Pottery Barn, placemats, odd shaped trays, shallow centerpiece bowls, and etsy should have a ton of stuff once you get an idea of what you want. Whatever you do, be prepared to return it, or use it somewhere else. Unless you are really good at combining art on a wall, it may take a few tries. Symmetrical candle sconces are a safer bet.