Mooncow - don't forget the ' in the long answers. They are backwards.
I found a website that factorises any number into its prime factors to get those last two. Can't see how you'd do it without some sort of help like that, which is a bit disappointing given the rest was doable without even a calculator.
I also have total gobble de gook and have spent a fair amount of time grid staring to no avail. Somewhat disappointing end to a nice puzzle, so far.