What type of "tung oil" did you use? There are many common "Tung Oil Finishes" that are not tung oil, do not contain tung oil and are simply diluted varnish. Here is a link that might be useful: About oil finishes

I agree, 42" is do-able for 4, but would definitely be on the small side. My 47" is quite roomy for 4, but I bet you could get away with 45" too.

Edited answer: For the rug, add 12" to each of the four sides, so a minimum of 9.5 feet square, but 10'x10' would be even better. General rule for table top space is 24" per diner. On a square table, you also have to account for overlap, so your table should fit eight comfortably.

nhb22, did you get your DR furniture through Vermont Woods Studio? If so, can you tell me which chairs you have? If not, would you share where you got them and the model? I have table and chairs from Vermont Woods Studio in natural cherry that look similar to yours, but my chairs are not padded and the backs on mine appear wider than yours. I am considering replacing the chairs for padded ones. Thank you!