I can answer a few of the questions, but it's open to other people to answer too...
From what I hear, they are looking for people that are going to be able to do the job, not just look at your CV and see how many qualifications you have. So if someone isn't suited to doing the job, then they probably get rejected. ;-)
Finally, the only other bit I can answer is that -all- RAF personnel will probably undergo weapons training, as you are an RAF Soldier first, and whatever your job is, second. If you can't fire a gun, if you need to, then you wouldn't be much use in a hostile environment.