Well as I said I had another playthrough and try to go only for headshots and I managed to finish the demo without any problem. The only thing I mention the "hint" system is that it's a demo. I've played lots of demos or being developed games and many of them don't have a "final" ending so you don't know when it finishes. So on my first playthrough I just thought the demo was to shoot around zombies.
In any case I liked it a lot and I hope to see it finished in the future ;)
p.s. : RE4 has a big difference in the village area, first of all enemies drop ammo and items and also it has a melee combat system that you can use hot keys to easily kill fallen enemies. Also RE4 has an adaptive difficulty system so if you fail it will be easier next time.