If I understand correctly, each event that constitutes training has a set percentage chance of increasing the corresponding skill.
I was a member of the 5th Army Rifle team, and as such, I did a lot of quality shooting, However, having already been pretty good, it was hard for me to get better, whereas I could easily add 15 to 30 points (7% to 14%) to the scores of relatively untrained shooters through an hour or so of coaching. What I'm suggesting is that the better you are, the harder it is to get still better.
Pseudo code might look something like this:
For each event which might produce an increase in skill:
If ( Rnd(100) < (MaxSkill - CurrentSkill) then CurrentSkill++
The higher your current skill is, the less likely you can increase it.
There was an earlier discussion from 5 years ago about whether bravery could increase by killing things.
Even though I was scared of heights, I went to Airborne school, thinking that would be the way to overcome it. Jumping from the 34 foot tower, I had my eyes shut every time and was dogged for it. I finally was so mad I psyched myself into thinking I would plant my feet in the Instructor's chest. Of course, I didn't get within 6 feet of him, but I was able to keep my eyes open. I had 82 parachute jumps over 21 years, and I'm still scared of heights.
I suggest that Bravery increase (limited as above by how close you are to MaxBravery) for each time you are wounded or are psychically attacked. In each case, if you survive, you know it's possible to do things you rightly should be afraid of, which is what bravery is all about. Killing things doesn't increase bravery, any more than shooting targets increases bravery.