Unfortunately, I think you can only talk about consciousness in the Neuroscience world if you have a Nobel prize. However, I think the argument still stands that it's a reasonable assumption that your entire conscious facility derives from the brain. Unless you want to make an argument for a soul, then it's fair to assume neurons and glial cells are the responsible parties.

Do we know for certain that quantum effects within neurons don't contribute to consciousness? No, but the most parsimonious answer would likely be that that's not the case. We have neither evidence nor reason to require such a mechanism to exist. What do neurons lack that cannot account for consciousness? If you can answer that, then I would allow the possibility of some other force in effect.

There are plenty of Neuroscientists who study parts of neurons, so it's not quite atomic, but overall you are right. If you take a patch of a neuron (separate it out from the rest of the cell) and record from it with an electrode, you can actually see random fluctuations in voltage that are unitary in size (that is, the voltage will jump in set units). What you are observing is the channels that conduct current, made up of proteins that span the membrane, opening and closing. These fluctuations are actually caused by random events in the dish. However, these fluctuations stop if you look at the same channels in an intact cell. What happens is the membrane of the cell helps to average out all of these random fluctuations. Thus, biology is relatively good at dealing with the randomness of Nature, and is unlikely to be affected by quantum fluctuations.