Terrain texture shows up as black when painted.

Hey y'all! I'm trying to paint terrain and when I do, the textures do not repeat as expected. Instead, they show up as one color, like spray paint.

For example, I'm expecting...

and it shows up like this.

The blurry, single-color result happens with any texture I paint onto the terrain. Any ideas? Thanks!

UPDATE from suggestions below.

First, I added a Base Terrain Material in the Terrain Settings. Now the ground textures appear as they should in the editor.

Then I used GPU-Z to determine if my graphics card supports Shader Model 3.0. It says it supports up to Shader Model 5.

However when viewed in-game there is a "static" that appears on the terrain about 10 feet from where the player is located. It dissipates as the player approaches the static.

This effect disappears if I turn on Shader Model 2 rendering in-game. It seems strange that I can support up to SM5.0 but 3.0 renders incorrectly in Unity.

Finally, the brick texture is better now but still looks blurry and overstretched.

I feel like this is user error. Any ideas?