In the case of AC, it's 1 for 1, so in your example 1 fighter against 3 bombers would leave 2 bombers. But yes, vs Torpedoes 1 fighter removes tho whole thing!
The key word in the rules with regards to ordnance interaction is "Marker". An AC wave may move and act as a single unit, but for the purposes of fighters vs bombers/assault boats, each squadron is still one "Marker".
For torpedoes, the whole salvo is considered 1 "Marker", regardless of strength. So yes, 4 lunars in a squadron combine their torpedoes into a str 24 marker, one fighter takes down the whole thing!
For this reason alone we use the following house rule:
Each fighter Squadron removes D6 torpedoes from a salvo, racial skills/expert pilots re-rolling. If a Target vessel has fighters on CAP, you may declare how may squadrons shall intercept the incoming Salvo, minimum 1 fighter per attacking salvo. Once declared, any surviving torpedoes will attack the vessel ignoring any remaining markers on CAP.
Hope that clears things up
