The domain of the function is from -128 to 128. The unexpected behavior occurs for input values less than -8 and between -2 and -8. The numeric bounds of this interval are -8 and -2.

[CODE]:

```
def f(x):
    if x < -8 or (x >= -2 and x < 0):
        return float('nan')
    elif x == 0:
        return float('inf')
    else:
        return -0.1 * x**3 - 0.2 * x**2 - 0.3 * x
```

This code approximates the behavior of the function by returning "nan" for input values less than -8 and between -2 and -8, returning "inf" for input value 0, and calculating the result using a cubic function for other input values.