Not sure if the roots are really everywhere , or how much sun/shade the area gets. I think a few shrubs near the back (probably planted closer together than "usual") would help minimize a tunnel feeling if the area is plantable. They'd need to be watered while getting established though. Although Limelights are hydrangeas, and hydrangeas have a reputation for being water-lovers, I have Limelights growing well and blooming in part shade where they get no supplemental water. If it's deep shade and you have a significant root issue (like maple/spruce), then that wouldn't work. Another suggestion is browsing the big boxes for some tough little crabapples. I got five "Molten Lava" crabapples on clearance a few years ago for $5 each. They're growing well in quite a bit of shade and with some root competition. Something like that doesn't get too big, but would also give you some privacy from the houses nearby IF that's an issue for you. (Not sure if this is a view you see from a window in your house.) Cheap, common hostas are cheap and common for a reason. They multiply well and are tough as nails. I second the suggestion to add some of those. Farmer's markets, if you have them, can be even cheaper than the big boxes sometimes. A great groundcover for that situation would be geranium macrorrhizum. It grows aggressively but is easy to yank, and forms a nice tight weed-preventing mat in most situations. I love free wood chips from tree trimmers too. I like the ones that aren't as finely chopped as others, since they last a lot longer, unless you decide you want to let them compost for later planting. I also like to get them in the winter. Without the green leaves shredded and mixed in, they don't decompose nearly as quickly. And if you find a trimmer who you can develop a bit of a rapport with, you can ask for hardwood chips for the same reason. You can often find "ditch lilies" free on craigslist, especially if you'll dig them. They're aggressive spreaders, but will bloom for a good three weeks in summer. Stella Doro or Happy Returns are also tough, nicer looking, and usually relatively inexpensive.

A couple of chairs and a table to make a small reading nookor better yet use that space for the DR and put a coat closet and a bench in the space where you now have the table because that space looks to small and is in the way of the entry.

Your plan looks good, but don't do a custom sectional unless you plan to live here forever. Maybe not even then. Have the sectional end where the kitchen begins. And I wouldn't use Barcelona chairs there. I love the way they look, but I wouldn't want to watch TV from them. Also consider a standard sofa instead of a sectional, and then where you show the chaise you could have an Eames lounger. Now that I would watch TV from.

Here are some ideas on how you could do up your corner space. As it is just opposite the entry door, you may want to create an entryway. You could add a dresser/ storage with some art above (image 1) You could also add a slim console and a couple of chairs (image 2&3). A decorative mirror may also be something to consider here. If you'd like more storage you can also use a tall bookcase like the one you linked above. I'd recommend one large bookcase as opposed to the 2 you were considering. Here's a link to an interactive 3D build for your specific room where you could try all these possibilities and more so you can visualize your room before you decide what to buy.