In reality, almost all modern games, even all the way back to 2001, use at least 1024x textures. Most, 2048x. I'm pretty sure one of the grass textures in here is a retiled version of the grass texture from Half Life 2 (Which is free to use, considering I modified it, fyi) Also, considering there aren't that many textures at all in FeralHeart, this should run on most medium to high end pcs.
Let me sum it up. If you can run Half Life 2, you should, in theory, be able to run this.