I'm not sure the weight if the car is with people in it.
I found the danish rules (which i suppose is pretty close to the eu ones) regarding weight, and it states that the weight of the car (in this example 1265kg for the abarth) is without any people in it and empty of fluids - so called dry weight.
That means you have to add the weight of fluids and people.
So the weight will more likely be around 1265kg + 20kg + 2 people (2x70kg) 140kg= 1425kg
If you type this in the calculator:
Power at Flywheel (BHP) : 170
Weight without Driver (KG) : 1425
Power to Weight Ratio (BHP Per Ton) : 121.21
0 - 60 (Secs) : 8.63
0 - 100 (Secs) : 24.72
60 - 100 (Secs) : 16.09
Quarter Mile (Secs) : 17.06
Terminal Speed (MPH) : 83.06
Drag Strip Quarter Mile (Secs) : 16.86
Drag Strip Terminal Speed (MPH) : 84.45
Which is perhaps more in line with the official numbers from Fiat.
Of course i could be wrong.
And the calculator doesn't take tourque, gear ratio, aerodynamics etc. in to account. But it's a fun toy anyway.