Don't know how old your son is, but it could serve different purposes as he grows. It would be a nice reading spot--rather than building in a bookcase you could do shallow wall mounted book racks (Ikea carries them). As he grows older it would make a nice desk/study area. And kids always love little nooks and crannies to play in, so a little bookcase could hold his favorite toys. I would consider having a wall mounted fixture wired now, though, as you need lighting for reading/studying. Love your windows!

I like pieces that are not matching though I find myself drawn to more classical styles such as the two Chesterfield loveseats in emerald green velvet, a wonderful wing chair in a kind of soft, almost sage green, and a rich cream sink-into-it chair and ottoman. The lamps are a mix of table and floor and modern and traditional. I would suggest looking at various styles of sofas online and getting a feel for what you like: straight or rolled arms, low or high arms, loose pillows on the back or none, and so on. Once you have narrowed down your choices to fewer than five, go out and try them out in stores. You don't have to buy from the stores but you'll get a strong sense of comfort. At the same time, think seriously about your wall color. You may want to stay with a neutral to allow a brightly colored sofa to stand out. Or maybe a dramatic color with neutral furniture (black paint, rich cream furniture in different textures and subtle shades). I definitely agree with no matching sets of furniture. Based on what I said at the beginning you can probably tell I ignore the advice to go neutral with the bigger items and bring in color with accessories. I love it because I took my time to discover the color I truly love and never get tired of: emerald.

DG is nice, but it's mostly dirt/dust, so probably won't make the difference you're looking for. You might look a different landscape rock. My dogs were never bothered by pea-gravel sized rock (though they sure could send it flying sometimes when on lizard patrol). Of the trees you are thinking of, I have them all. I'd do a fig unless you want winter shade (they are deciduous). Figs require the least water, don't particularly care for fertilizer, and grow the fastest. Citrus stay green, but they grow the slowest, can freeze in winter, must be fed regularly, grow best as a bush (you have to protect the trunk), can be prone to disease, and require a lot of water. Poms are nice, but they don't get particularly big and you have to water them consistently or the fruit will split. Have you considered any native trees that might be even easier to live with than a fruit tree? And there's always shade sails.

Take a few pictures of the ENTIRE space. Several angles........ My bet is the garden projects need to move to the nature outdoors.