IMO, 3 would be adequate, with 5 you could go with lower wattage bulbs and not have it too bright. You can find many 5 bulb fixtures less than 26", depending on the style that you want. Style would also determine where the bulbs are pointed. With a clear glass fixture and clear bulbs, it tends not to matter. BTW, have you considered how you will replace the bulbs in the stairwell? Here is a link that might be useful:

oh I looked into slate,porcelain, ceramics, you name it. Loved slate (the solid darker one) etc. My main concern was with the colors. Given the existing/known colors are decided upon . Darker slate(and travertine)-the one I like the most-will it be enough contrast with dark cherry island? Lighter-will it work ok with the countertop? Should be fairly warm colored too. I don't see grey here. Something like Linden looks like it'll work. The main point though-one goes, takes samples, starts comparing. It's hard to see materials on the internet.. (choosing flooring was one of the most tiresome thing as far as I remember. That, and countertops.) I also think the floor -if it mimics stone or is stone-shouldn't be too busy as the countertop gets to be busy already. Then you have two busy stones If it doesn't mimic stone but has pattern in how it's laid-I'd worry about how to clean it, but less about busy-ness..somehow spells farmhouse to me, more than busy countertops.. Something put together as longer, brick reminding tiles on diagonal would be cool. I see more uniform, darker tiles if going for that look. Slate or porcelain, doesn't matter as long as it's right color. But. One can't get everything I guess. I love the idea of soapstone but probably more upkeep? But they look amazing, and very true to farmhouse feel.

Are you planning to keep the yellow? Nothing wrong with it, it looks like a happy color :), just wanted to say that if you are planning to paint then you should probably pick those colors first and paint before putting down new flooring. Are you looking for more of the plank look or a tile look? There are so many options available in vinyl flooring. (Congrats on your new home btw)

"I thought I wanted super plain wood railings and basic square balusters." Go with your first gut-level instinct and find something that best complements the design style of your house. I've always found that to be the best choice in the end. The 4th and 6th photos from the top are closest to that idea, and I like it.