Do I have a medical malpractice case in the death of my dad?

You have our sympathy for your loss. Unfortunately, you most likely do not have a case.
First and foremost, whether something is malpractice is not judged by current medical knowledge; it is judged by what was known *at the time* the procedure was done. Malpractice is providing medical care that does not meet the then-currently accepted standards for care. Medical care improves over time--to use an extreme example, during the Civil War, amputations of gunshot limbs without anesthetic was considered the best care, but nowadays, we know far better. Civil war surgeons who cut off gunshot limbs were not doing malpractice; they were doing the best they could, even if we nowadays cringe at that treatment.
Similarly, if 30 years that fluid was considered a safe and appropriate diagnostic tool, it was not malpractice to use it, even if we have learned better since then. So you'd have to show that 30 years ago, it was considered risky or dangerous to use that fluid in order to potentially have a case.
Second, even if the use of that fluid was already being questioned 30 years ago, you'd need to be able to prove to a reasonable certainty (i.e. by a "preponderance of the evidence") by medical evidence (e.g. by the testimony of doctors who examined your father, who linked, based on medical evidence, his cancer to that fluid) that cancer resulting 30 years later was caused by that fluid and not by other generic or environmental factors, and that can be very difficult to do.