I only kill off high-level characters. And I usually do it by giving them lots of rope to hang themselves with.
B/X is brutal. But it's not usually
this deadly.
One more comment, then I shut up for a while (maybe): I suspect that part of the overpowering deadliness of this game is that Dave is used to Pathfinder and AD&D 2e, which have a higher power level than B/X. The armored second-level fighters, the wolverine, and the crab are examples of enemies that might have been fine in a Pathfinder or 2e game for first-level players but are completely overpowered against first-level BX characters.
My parting suggestion: if you decide to start up another BX game sometime, try making it an easy game, using only monsters in the BX books. If it really does end up being too easy (I have my doubts), you can always turn up the difficulty level. It's hard to reduce the difficulty when everyone's dead.
