That's a little wierd. Not sure how its all calculated but I used my 3w to buff its power for a round instead of my driver and I was demoted when done. I went back to my driver the next round and went back up.
Yeah, same clubs except now they're broken. I thought using a broken club would help me hone my skills and instincts better since they don't show you where the flag is on the meter. Ah well.
I went back through after finishing the story (vs) mode and got my gallery filled... rank never went down. The only time it happened to me was when I used my 3w the whole round instead of my driver.
It goes up and down depending on the course you are on easier courses you must do extremely well with no bogeys harder courses same thing but they are a little more forgiving. That being said I don't really see any benefit from your golf level at the moment. I go up and down daily but don't really see any difference unless I'm missing something