Hi Gille
Sounds as if you’re playing Global 40 ? Or Pacific or Europe 40 ? Anyway Global takes a long time. Probably need a weekend to get through it.
For Strategic Bombing Raids, you can only intercept with fighters that are in the territory being bombed. Your factories and bases have built in AAGuns. Each Bomber or Tac Bomber that makes it past any Interceptors will undergo “1” AA shot before dropping their bombs. So the ones you use in normal combat don’t fire.
You can only scramble up to “3” fighters or Tacs to an adjacent sea zone as long as you have a operational Air Base. If Allied planes are present they have the option to scramble as well. You still can only scramble 3 max. For Interceptors above you can send as many as you have.
You can only use your own units to attack with. Allied units do defend together.
I’m sure someone else will chime in with a better explanation