There is a massive difference in power, if you speak of F3000 as FIA homologated cars up until 2004...
You are comparing torque from DFV (early) or Zytek (90's) 3.0 litre V8's for the F3000 (hence the name) to Abarth's spec of 1.4 litre engines with only 250nm or so of torque.
On slicks and with "play nice" difflock and suspension setups the FA is not going to do anything unexpected. It doesn't have the power to relly bite you.
The F3000 as FIA spec'd it is however a different beast. If it starts to slide, the difference in torque alone is significant, as well as some aero differences.
So, i would say the behaviour of the FA seems reasonable to me. It behaves a bit like the lower powered Radicals do, that i have experience in IRL, and i think it seems to be accurate for what it is, having never driven an FA.