These appear to be west elm circle cut out chairs. I don't think they in the online catalogue anymore, but I did a quick search and it looks like some sets are coming up for sale on other sites.

Don't put a stool there! Find a tiny little bookshelf that will just fit in the space underneath - that way you can't tell that there's supposed to be that extra space there?!

Chantelle, what a fab table! I can't tell though if the top is timber, stone, concrete (or the look of) or metal. If you like industrial style then Oskuee's top three images are perfect! The fourth photo is a crossback chair which can suit industrial, Hamptons and modern country. However if you like a modern classic look, then a fully upholstered chair like the style of the one in this link would work. Either colour match the legs to the table or paint them matt black. A straight leg, rather than a taper ( as shown in the link) might be better too. Fabric-wise because the table has clean lines, a self pattern or plain would be best. Photos please when you're finished. https://www.houzz.com.au/photos/custom-designed-dining-table-and-chairs-contemporary-dining-room-sydney-phvw-vp~55535654

From what you have said, I think smaller separate pieces such as couch and chair(s) rather than a large sectional is likely to work better in the space and still allow for traffic flow. However, if you still have lots to do then don't rush to make large purchases. In the meantime, if your current sectional looks better pulled away from the wall a bit, then perhaps you could rotate the side table so that the long side runs parallel with the sofa arm instead of the wall. Would that help to stop it blocking the doorway and resolve the 'not quite right' placement?