I don't buy that story. There has never been anyone contracting HIV in a fight.
I am in the same situation you are in.
And, also, does even for theoretical risk there must be large amount of fluids?
No one really knows the answer to your question. Most sites state theoretical risks of passing HIV, such as through little cuts, etc., but there's never been a reported case. Theoretically it's possible, just like theoretically, it's possible that when you walk outside today, you may be hit with a car.