advice on running

There is a ton of options, I know many runners run 5 days or more a week. , have you been compleatly injury free? How long have you been running? What is your running goal?

Three days a week is great! You can replace one of your runs with fartlek training (speed play) or hill repeats, but it really depends on your overall goals. Every run doesn't have to be full out for 30-45 minutes.

Slow progression, adding only small amounts of distance or intensity is always safer. There might be a good local running club or running clinic?

OK, seems to be that time of year.

First, get to your recruiters and find out the standard that you're supposed to have for the entry test, and the standards required for the in-service test that you'll need to pass once you're in new entry training. Train towards the latter and you'll be able to smash the former.

For my own service I'd suggest getting to the stage that you could run 10km comfortably before entry, and do a fair amount of bodyweight work in preparation. There is little work using weights in new entry training, it's predominantly about moving your own weight around.

For the running, use a Couch to 10K plan as the basis, but you may want to make some changes subject to where you are at the moment. You get much more from lots of easy distance miles, than going flat out. fwiw being able to run for 10Km should mean being able to pass the new entry test without flogging yourself.

As far as pre run fuel is concerned, I'd aim to train to run fasted. When I was in training we did most of our running before breakfast, so condition yourself towards that.