Hi Imperez... i ran out of thoughts for you ...
I am glad that you are excited and happy and from your first posts i can say that you are much better informed by now.
If she is expecting puppies from different dad's or there are a few days difference between them they will be born showing differences... that is usually what happens with a tiny runt, that happens to be 3 up to 5 days younger than the big sibling in there.
I am sure you are doing your best and you will be a good helper for her.
Her chewing can be from "pain' as contractions become more frequent and stronger. they actually shred paper and little towels during deliver. Scratching, chewing and nesting go together. She may be just chewing.
wait and see is the only thing you can do now.
Xrays usually start showing skeletons about 42 to 46 days, at 50 days you really can see everything calcified. But that is guessing.
I am with you, i think someone saw her mating... and they could at least let you know the exact day, it will be a great help.
But i doubt they will say anything do you?
XOXO