The ammo stash doesn't refill. You only get refills from the Cedar Box.
But you're not in trouble yet. You can use the knife on Ghouls, and there's still enough ammo left on the coming levels to take out the occasional Nightmares.
Two tips on dealing with Ghouls with the knife:
1) They're left-handed, so if you meet several in close quarters you want to be standing to your left of the one in front. The ones in back can throw around their left (your right) of the one in front, but not the other way around. (Don't worry about them shooting "under the arm" of the one in front. Enemy bullets, including rocks, treat other enemies as pillars reaching from ground to ceiling. The size of the pillar need not match the size of the sprite the enemy is drawn with; in particular, you might see arms and legs sticking outside the pillar, if you could see the pillar. All monsters are the same size pillar.)
2) Don't just hold down the fire button and let the knife automatically stab again. Its auto-fire rate is too slow. You need to make explicit individual stabs. There's a rhythm to it. Listen to their grunts, and stab in in time with them. You may see a rock materialize in their hand during a knife fight, but if you have the timing right the rock will disappear before they can throw it.
And a special tip for starting your descent:
Turning off your flashlight lets you get closer to them before they notice you. In particular, on Wrong Way (first level below Ground Floor, but not the one crawling with Oozes), there are two ghouls in each of the four corners. If your flashlight is off when you enter, and you're careful, you can wake them up two at a time. Run back upstairs and save after killing each pair. Get to the ladder by backing away from the corner you just cleared, so you don't face corners that still have Ghouls in them. (Seeing any part of a cell next to a monster wakes it up. Waking up a monster wakes up monsters around him.) Fighting two ghouls at a time with a knife is doable. Trying to take on all eight at once in an open area like that is suicide. Once you clear out that room, there's a dead Nazi in there who will give you more ammo. Save the ammo for Nightmares and maybe Zombies. Don't waste ammo on Ghouls. There's a lot of ammo on the next level down (Welcome Tasty Primate), but still not enough to waste.
