A fair effort
Not a bad attempt. And frankly, this being "The Portal" you can bet it ranks better than over two thirds the worthless crap on here.
The game was too linear, even if you just make it so that you can pass certain parts by ignoring them (Like the zombie in the closet) I'd probably bump you up a point. It'd really add an element of strategy to the game. "Do I risk fighting the zombie or pass up the shotgun?"
The effort you did put into it shows. No one's faulting you for that, or the result. It just needs a bit more tweaking.
Some people might complain about the healing in between fights, and the ease of defeating the monsters. I think there's nothing wrong with having each combat start "fresh" but the healing during the fight makes it more like a "grappling" game, where one increases as the other decreases. Again, not a bad idea, but it doesn't work here because it's too easy.
How about if instead of action clicking, you turned it into "dice rolling"? With each weapon having a damage and ease of use. Since the zombies all attack close range, this would make the knife more preferable to the gun for ease of use, yet the gun does more damage. I DID, however, like the ability to select the weapons before combat, and the fact that at some points you did have more than one to choose from. Variety of weapons = good. The bullets also added to the fun factor by allowing you to keep a used weapon longer. With more diversity in combat, and a more challenging atmosphere, this could really be one of the games selling points.
Overall = 6 + 1 for the obvious effort