Your home looks lovely. Ideas that come to mind for your 'dining' room include a sewing room, craft room, reading nook or children's playroom with a day bed but any of those ideas will only work if you have use for them. I know you have said you don't want another sitting room but my instinct would be a pair of wicker chairs, a jute mat, a small side table and some indoor greenery - essentially making a summer sitting room/reading room. With regards to your coffee table, perhaps include some texture. Either a mat under the bowl or fill the bowl with brush balls or something similar. Otherwise it appears to work well with your other furnishings and style.

It all depends on how much money you would like to spend. As your lounge is dark and your stools and bookcase are also dark I think white chairs would be fine, but then I would change the stools as well and take some white down to the lounge area. However you can buy stretchy covers for this style of chair for around $10 and there is quite a variety, so I would look on line for those to see if you like any of them as that would be a very easy fix.

The structure to the viewer's left is the alfresco area with the main house attatched to the right. Hopefully this gives you a sense of the space internally. The french doors to the viewer's right lead onto the alfresco area. Ideally, I would like to convert the existing front living into a bedroom, with an enterance hallway leading to the open concept living (current kitchen/dining in photo) with large new kitchen/dining in alfresco. It would require removing the current wall with french doors etc....so engineering of this will be needed. And finally, this is the view into the space from the back yard. The timber structure to the viewer's right, is the existing main living/retreat area. Hopefully, this helps!

If your tv is 65” then the lounge is way too close to television. Place lounge as per my diagram. Two lounges in L shape plus single chair. If you remove the small wall then dining table can be across room. But it may be load bearing, so unable to be removed.