its still a bit too hard as one bomb from a skeleton is instant death and they are very quick to spot you and throw a lot better than you ... i havent even been able to reach the key for the first door yet after half an hour of play !
That's weird, I haven't encountered that issue. The only thing that insta-kills you is the acid.
Keep in mind that all potion explosions damage you, and you take damage (1 heart) if anything hits you while carrying a potion. That might be why you're taking multiple hits.