I can only imagine that he's describing a Benzodiazepine along the lines of Clonazepam (Klonopin), Alprazolam (Xanax) or Lorazepam (Ativan) given the dosage increments, but it's anyone's guess really. We know Lorazepam is approximately half the strength of the previously mentioned two drugs, so why don't we do the safety dance and assume that he's taking of the most powerful Benzodiazepines available.
Dosages go lower obviously, but .5mg is typically the jumping off point for Benzodiazepines of this strength. With that said, taking any, any at all, Benzodiazepine with Alcohol is deliberately seeking out trouble for yourself. I don't care if the dosages are "reasonable" or not. You must prepare yourself for potential consequences, which could include blacking out, driving a car and killing somebody. I don't mean to dampen the mood or anything, but this is a reality and it happens.
Given this, "worst case scenario", this is about what I would consider a fairly responsible intake. I feel at this level, you are straddling a line that could easily be crossed into the territory of blackout. In case you're not familiar, blacking out and passing out are different. In a blackout, you are typically still moving and acting. Be careful.