A) Many of the early manufacturers had their own glass recipes and made batches from scratch - they didn't use cullet.
BB) Very small quantities of uranium were used as a colorant (yellow-green) and uranium glass objects do emit very low levels of radiation.
C) This is a very complex topic but here is a general idea . . . Different substances in glass can fluoresce and each responds maximally to UV of a specific wavelength and emits certain wavelengths of visible light in response. The UV lights sold for consumer use emit light in the very upper part of the UV range. Lower wavelengths can be dangerous. The spectrum of UV different lights emit can vary depending on the source, e.g., fluorescent vs LED. The intensity of the UV emitted by different sources can also vary. Together, this is why some lights produce more of a UV "pop" on a given marble than others.