It sounds like BK channels interact with NMDA receptors, which are glutamate receptors. Glutamate is an excitatory neurotransmitter. My understanding is that inhibiting glutamate is partly what makes alcohol relaxing (the other is it's interaction with GABA). Bodies have an amazing way of keeping themselves in equilibrium and when someone is introducing alcohol into their system on a regular basis, I figured that the body regulates this by increasing levels of glutamate (although maybe also via downregulating GABA receptors), so that the person stays awake even with higher doses of alcohol. I do think that this can lead to someone having a higher "tolerance". I also think that's what contributes to what some people call hangxiety, i.e. there's still extra glutamate floating around that wouldn't otherwise be there.

However, an enlarged liver helping someone process alcohol better sounds bizarre to me. I thought a liver being able to process alcohol faster was due to increased enzymes since the body again is trying to balance itself and is dealing with what is being introduced by upping certain enzymes, whereas in a non-drinker, those enzymes wouldn't be at elevated levels.