Let’s say, the guy who tells you what to do could go a little more into detail of what you’re supposed to do, but otherwise its good the way it is. He says that thing can hear you, so you probably think you can sneak past. If you can’t, the design is in some way flawed. Maybe you should get a little hint on how to distract the tentacles.
As for the backtracking, I remember figuring it out when I first played Half-Life. I admit I was confused as well, but Gregorovich! pretty much got it to the point. You must examine the environment, think and then act, something which distinguishes the Half-Life experience from modern shooters! And to be honest, I can’t quite agree with the complaints about the tentacles. Like lucifer said, you don’t really wanna stay in that room for long anyway. Rush through the room, keep throwing grenades and the tentacles won’t hit or even notice you.