If you're shooting RAW WB can be adjusted in post so it's not critical, but can save time later on. That is if you shoot in RAW, that's your decision, I however would not consider NOT shooting RAW.
The last airshow I shot jets typically at 1/1000 or faster typically at around f/8 on AI servo, as others mentioned. I don't recall the ISOs used but probably stayed at 400 and maybe up to 800. On prop planes and helicopters you typically want to slow down your shutter to around 1/250 for planes and 1/160 for helicopters. This is so you get the blur of the props and not them frozen in air. The slower the better but at some point you'll have diminished sharpness due to your panning motion and/or movement of the subject.
Agree with those that say stick with the 75-300. I'd personally like to have a max FL of 400mm but 300mm is the longest you have and it will do well for you. Just realize that your lens is not of the highest quality so your IQ may not be the best . I'm not trying to discourage you but you should just be aware of it. If you really wanted a good airshow lens you'd have to spend around $1500 for the EF 100-400. If you have the money to burn I'd recommend you get that but if you don't just realize the $1500 lens will give you better pictures.