For the experts - might Vyvanse (lisdexamfetamine) effect my blood alcohol level?

No, not directly. Vyvanse (lisdexamfetamine) can increase some digestive and metabolic processes, but it is not likely to have a significant effect on the blood alcohol level. Due to enhanced alertness, some may feel less impaired/sedated by the effects of alcohol, but this is illusionary -- excessive alcohol intake will be just as problematic. In fact, it may be worse since the vyvanse (lisdexamfetamine) may impart a sense of misplaced confidence.
It is doubtful. that there would be any significant change to actual blood alcohol level. But it is recommended that alcohol & vyvanse (lisdexamfetamine) not be used together due to ^ risk for ^ heart rate, blood pressure changes or chest pain.