Your plan to spend more time getting the area ready sounds very reasonable. Even if you don't add a bunch of 'dirt' or amendments, by making sure the weeds you pulled are dead (and not going to grow back from the roots as some plants can,) you can expect a much easier time after you do start to put desirable plants there. Weeding never ends, the wind blows seeds, and birds and squirrels move them around constantly, but once you get things under control, it should be very easy to notice wayward sprouts in such a small spot and pull them while they are still infants and come up easily. Since there are tree roots there, I might not add anything but some mulch. That helps moderate moisture levels, in both times of drought and pouring rains. It also makes it harder for many unwanted sprouts to even get going, and easier to pull if they do. An organic mulch that decomposes over time will also add a measure of fertility to the soil, as well as improving the texture. Leaves make a fine mulch, though the cost of a couple bags of store-bought shredded wood (not painted, or with anything added,) would be reasonable for that small area and always looks fantastic, 'finished.' You could sit the pots there on top of the mulch while you're waiting to see if any of those roots keep growing unwanted plants. When planting around tree roots, I don't try to cut through the big ones you described, though doing that to a few in such a small area won't hurt the tree (or shrub) if you need to cut some to be able to use the space. Cutting them a double-edged sword, since it will usually cause many more roots to grow from the end that's still connected to the tree or shrub. When planting perennials (plants that come back after winter,) it's not as much of an issue as it is in a spot where you want to be able to dig holes for annuals (plants killed over winter) annually. A happy medium where annuals are preferred might be planting some seeds, which can find their own way around the tree roots. The seeds sold at seed racks are mostly fast-growing annuals that reliably have time to make flowers well before danger of frost (assuming they are sown when/as directed,) hence their enduring popularity. Marigolds are in this category.

I do not sell my candles but I give you some tips on making them; 1)Use good quality oils to begin with. If you haven't already done so, you will need to get some samples of oils & wicks, to test them. 2)Measure, measure, measure! 1 oz. of oil per pound of wax is generally accepted as a safe, effective ratio. 3)Monitor temperature. Add scent around 180 degrees F. (Too hot & the scent will evaporate) Pour at around 100-110 degrees F, so you will not crack the glass and the top of the candle will look smooth.

What is the diameter of the containers you use? If they are very wide-mouthed, you may need to use 2 wicks per candle.

I'd center a sofa table under the window, with either some plants or lamps on it, and then push the sofa up against it. With all of those built-ins, you've got ideal toy storage, game storage, blanket storage, more than enough storage, and even better, it is behind doors. Once the couch is pushed back, you can experiment with the chairs, either flanking the fireplace, or flanking the couch. It's hard to tell what exactly will work best from the photos. Are those vertical blinds on the large window? We have a window very similar to that. Our home came with vertical blinds on the picture window that drove me bananas! We replaced the blinds with a single solar shade that rolls up and down with a chain; so much better! Our couch sits up against the window and we can now close the shades without climbing on the couch. (Pictures here.) You could do stationary curtain panels on each side of the windows. I like your paint and trim colors. It looks like you might be gravitating more toward lighter, brighter colors, so you could paint the built-ins white and lighten the space (the wood will be more forgiving of little ones, though...)