Single Channel ADC with DMA giving garbage results on STM32F7
It isn't a 32-bit ADC yet you are interpreting its outputs as UINT32.

Looking at your idle codes for example, 131073 = 2 ( * 2**16) + 1, or 2 and 1 if they were packed UINT16,

So those values all look fine to me.

I could do the same for the "3V" values but I'll let you do that.