You can deal damage to enemies by striking them with or throwing objects found on the ground, as for weapons, you can rotate them using the 'R' key and attack with the left mouse button. The reason you sometimes walk slowly for no apparent reason is that your paranoia level rises in the night and in shadowed areas, whereas it returns to normal in the morning. And the reason you're stuck frozen on the ground is that I forgot to create the death screen, the bar in the bottom-left corner is your health bar, and it refills every morning.