Not sure I’m completely convinced by your theory, Baldwin hedgehog, about big poos meaning a female has babies nearby. I think it could easily be misleading. Some hogs naturally do bigger poos than others anyway, so not sure how you would differentiate.
The reasoning sounds ok on the surface, but if the hog spends more time in the nest, then why couldn’t she just do more of the same sized poos and, also, she would probably be eating less food than normal.
But, I hope, for your sake, you’re right and hoglets are in a nest nearby.
Re. the cat biscuits. You shouldn’t really need to crush them. If you are worried about the hoglets not being able to manage them, you can always get kitten biscuits. If they are uncrushed, they can help to keep their teeth clean!