I understand your wish for closure and I believe you should speak with your OB/GYN physician or midwife or Nurse Practioner, whichever you have as your treating OB/GYN. Tell this professional about your concerns. I believe some grief counseling is in order and can be of great benefit to you.
When you suffered the miscarriage, the fetal material was most likely completely discharged. What remained was placental tissue and the increased endometrial tissue, also considered part of the products of conception. Even if part of the actual fetal tissue remained until the d&c, it would be nearly impossible to differentiate the minute fetal tissues from the placental and endometrial tissue (uterus lining), as it is all collected through the same instrument and into the same container.
The hospital and its employees acted appropriately. The pathologist is going beyond the norm in providing you with the parafin blocks. You can not force him to give you the slides for burial, nor should you.
I suppose you could have instructed the physician to give all of the products of the d&c to you for burial (except for the pathology needs); but, you would have needed to provide these instructions before the procedure. Otherwise, the physician would have no way of knowing that you wanted to bury everything possible. I assure you, most people do not want to have these products for burial unless the fetus is well developed and not in the earliest stage of development.
I imagine the law (to which you referred) is intended to prevent abortion clinics from improperly disposing of fetal remains.
To find closure, you need to accept that all was done as it should have been done and that you have done all you can do to provide a proper burial for the remains.
If your grief does not lessen in the next few weeks, please consult with a counselor or pastor.
Best wishes and deepest sympathy for your loss,
Not All Who Wander Are Lost. J. R. R. Tolkein