Hi man , first , i am not sure about normal and impact normal ,
even here i cant figure out. you have to try both.
I have a simple actor that take a front and back coords. taking my location and adding and subtracting a forward vector and a forward vector*-1 . So now i have Head and Tail , thats are 2 location Always placed.
From these 2 points i call the line trace for channel . visibility. to get the location where start the ground.
Now i have the Coords of the ground under Head , and under Tail.
I take these 2 vectors. and subtract the headground to the Tailground . (or viceversa i dont remember)
This will give you a middle direction of the ground. you want the dog look toward this direction.
So rotate the dog .