Sunfyre7896: how long, I guess in full rounds or holes do each ball last per one whole dot on their stats
The durability can vary a bit between different types of balls, even if they have the same number of dots. However, as a rule, I think: 1 dot = 90 hits; 1.5 = 110 hits; 2.5 =125. (a player named racoondad has a detailed chart on his profile page; find under WGT community>players>(search) The actual number of hits has been counted).
A "hit" is any shot that is not a putt. I figure a 9-hole round is around 20 hits.... you may well have more -- or a few less. (9 tee shots; 7 approach shots; 1 more for a par 5; 3 chips & pitches for missed greens = 20; plus 15 putts = 35).
So, a ball with 1.5 durability (110 hits) will last about 5 nine-hole rounds, assuming you don't lose it.
Sunfyre7896: Secondly, when the balls begin to deteriorate
The balls don't deteriorate in terms of performance, they just run out.