Thanks for the reminder that local requirements may differ; I should append that qualifier to every posting in small legal print. The pertinent North Carolina Building Code Section is: "2304.11.2.2 Framing. Wood framing members, includ- ing wood sheathing, which rest on exterior foundation walls and are less than 8 inches (203 mm) from exposed earth shall be of naturally durable or preservative-treated wood. Wood framing members and furring strips at- tached directly to the interior of exterior masonry or con- crete walls below grade shall be of approved naturally durable or preservative-treated wood." (emphasis added) I would suggest to the authority having jurisdiction that an interposing section of XPS means that the wood framing is not "attached directly".

Okay, so the first photo above is the piece that broke off. This picture is the blocks where the glue let go--you can see it looks a little bit reddish compared to the dark stain, adn you can just see the outline of the blocks where the glue failed on the picture above. I should note that the blocks on one side are quite close together, as in this picture, and the blocks on the other side have quite some distance between them, which is the side that you see on the table, hence the wider space between glue stains.

It has been my experience that if a really good match---like with the Stain Putty---is not possible---like trying the color sticks/sawdust and glue/---making the filler lighter is less eye catching. I did several hundred feet of pine crown molding, stained dark walnut. The home owner specificially mentioned he wanted no conditioner---he wanted the color differences from the stain to show. And with even good stain grade pine, there was a LOT of difference. It was in a room with 7' ceilings and a soffit for HVAC in the center the length of the room that was 10" below the ceiling. I used a 16 gauge nailer and had a lot of nail holes to fill. I made up two batches of Stain Putty----one with the dark walnut stain and another with pecan stain. The dark walnut Stain Putty was a perfect match for the darker areas---but would have stood out like a sore thumb on the lighter areas. The pecan was a bit lighter than the light areas and was a fdair match---the HO could not see the filled holes----and he is a professional painter---has owned his own company for 30 years.

I understand your goal, but there is not a perfect solution for this. The existing finish is most likely (but not certainly) lacquer. If that is what it is, lacquer will bond best with it. I would not try to make it perfectly level with the table surface but just a smoother, less deep crack. Test whatever you plan to use on a small, preferably obscure area first. Here is a link that might be useful: crack filler