I really do hope know the errors of your way.....
If her diet is a good quality kibble, then I would say adding extra calcium supplements would be dangerous, but considering she is a baby herself and still growing herself(well, not anymore, growing and matureing will now stop), the extra calcium would be necessary.
X-rays(also known as radiographs) are not bad for the pups. Its used to detect abnormal amounts of fluid or organ enlargments after the 45th day of pregnancy.
As she gets further through the pregnancy, we can fill you in on info needed at that particular time, cause there are plenty of things to take into consideration.
Breeding is much harder than it seems!
Please start saving money, there are plenty of hereditory problems that can go wrong including 3 joints and hip conditions, 5 possible eye conditions, epilepsy, deafness, allergies, heart conditions plus more I can't think of right now. Oh, and emergency C-sections. My favourite one to share that I have been involved with. $7,000 for a C-section to have all but one puppy die. Registered, responsible, planned pregnancy. Beautiful dogs, beautiful owners, did everything 100% correct, and things still can go wrong.