mallyh - I love your answer but there are no 8-letter grid possibilities. (Nor are there any 6- & 7-letter spaces, but plenty of 5 & even four 9-letter possibles.)
Tested out 'nod' and it provides the right answer to the whole puzzle. Only problem is that there are eight 3-letter possibles. The combination of 20, 18 appears twice & that helps.