Naïveté knows no boundaries

For your first question,  that number for the lack of a better description is your “power level”.  By that I don’t mean how far you hit the ball, but how good your golfer is overall.  99 is the highest achievable.

For rewards points, the answer is yes.  Do challenges, accomplish quests by playing career mode, and do the daily free tournament and make sure you end with a win or world rank (this usually means playing it until you birdie or eagle every hole of the 4).  When you get to a higher skill play the dailys that provide tickets,  and use those tickets to enter weekly’s for bigger prizes.   Also,  do the pro pass quests as well.  

For the last question,  I’d say probably not for no other reason than there is no putting specs and even if you put 10 into putting it only fills your putting power by like half…