yes the number of fighters you need is very dependent on the generation. You also can only target per squadron 6 small craft, the question is more how many of those 6 do you hit?
The sequence will be: 6 fighters fire, 1 small craft fires back, 6 fighters, 1 small craft,..., last 6 fighters fire, all remaining small craft shoot back. All fire will be first directed at a squadron that has not fired, and then a la carte I'd say.
The number of fighters that survive the small craft fire is stronly dependent on how many movement points you can stick into evasion, and the chance you kill a small craft is determined by if you use guns (though that means you must enter the envelope of the small craft) or if you try and use fighter laser and stay at extreme Db range, but that means you must target the Pn first to get their D out of the equation.
I don't like using fighters for this because you are trading expensive fighters for effectively dirt cheap small craft. But it is hard to argue that the fighters aren't your best way to deal with them assuming you have enough fighters that is.
I also agree that before you commit your fighters except as a last ditch defence a rule of thumb of 50% of the small craft isn't too far off. The fighters only real advantages are you fire on 6 small craft at a time, and the +1 to hit you get for firing on a small craft. It is one of those brutal attrition battles governed by the equations: the loss rate of side 1 is proportional to the strength of side 2, and the loss rate of side 2 is proportional to the strength of side 1.
example: assume F1 with fGx3 x60 against 120 ast. Chance of a fighter to kill the small craft is 95% or so. Chance for the small craft to kill the fighter is 30%. Assume 0 range.
Round 1
60 fighters will kill 57 small craft (Ignoring in this case fighter losses during the fighter fire phase)
120-57= 63 + 9 (for small craft that fire during the fighter fire phase) = return fire of 72*0.3= 22 fighters lost
Round 2
38 fighters will kill 36 small craft (...)
63-36= 27 + 6 (for small craft that fire during the fighter fire phase) = return fire of 33*0.3 = 10 fighters lost
Round 3
28 fighter will kill 26 small craft (...)
27-26= 1 + 4 (for small craft that fire during the fighter fire phase) = return fire of 5*0.3 = 2 fighters lost
so 60 F1 with gun packs engage 120 ast at range 0 and in 3 rounds the fighters should win with 26 fighters surviving...I would say this is + or - one round and losses should be good to the tendancy of 20-30 fighters survive. But you can do something similar with differening numbers to see what you can maybe get away with. However in reall rolling this will be governed by binary statistics and well odd stuff can happen.