On 2) above why not just click a setting lighter on the campaign setting in workshop?
Regional Air Activity setting in Worskhop.

It's optimized to produce less of a range (smaller regional activity) circle of operations so scales automatically based on many complicated factors (there are many, one example is 'are there enough squads in the region etc to produce a war') it doesn't break escorts or other missions, and will reduce flights and also the numbers in the flights too to help with CPU load.

In future, we will likely add a visual indicator - circles to show the already-built-in regional activity and operational area controls where AI is active. Also we have more than 1 circle in use for various reasons.

On long range missions, for example Gotha raids, you also need to cope with the fact you may be flying to another country to fight - so culling flights based on a small circle will kill that campaign mission type.

There is also always a chance you will be ambushed so not sure why you need to add more, there are real flights on patrol not "spawned",
Heavier activity will give more chance of seeing enemies or being ambushed of course.