I can't answer all the questions as I still don't know here's what I do know.
My guardian has a 5436 build (I don't know how before I awoke it, it was 4325, and after it magically grew a point everywhere). It has 5 power skill slots, 4 magic skill slots, 3 sense skill slots, and 6 charm skill slots. I have only been able to teach it 1st job charm attack and debuff skills. I tried teaching it card strike and impelling rage but neither took, I also tried shield all and dodge master but neither of those took. I was able to teach it titanium wrist but not physical training. My fox friend said hers wouldn't learn gun skills. and when I put my mastered skills on my guardian they show up lvl 10, and to remove them all I have to do is right click them.
That's what I got so far.