Off season question

I just finished my first season with the Celtics, and won the championship in 6 games vs the Lakers. Antoine Walker was the league MVP, Tony Battie was defensive player of the year, and Walter McCarty was 6th man of the year. Paul Pierce was Finals MVP.
Here are my questions about the off season.
1) What makes players refuse to resign with your team? Kenny Anderson refused to resign with me, even after he was the starting PG and averaged a lot of assists per game.
2) What constitutes (stats?) a player wanting to get an increase in salary?
3) What causes players to decrease their ratings into the next season?
Antoine Walker was the MVP of the league in the prior season, yet his overall rating in 03-04 is 88, and in 02-03 it was 90. Why did this happen? Is it just age??? Not all players get crappier as they get older.
I've noticed that while playing games in the new year, it seems that players are slower than the previously were.

Players refusing to re-sign can be quite random, and is based on how they feel about their role on your team, their chances of winning a championship, etc. I couldn't tell you the formula the game uses to determine that though.

A player's salary depends on his overall rating, so a player in decline will usually warrant a lower salary, while a player in his prime will demand the big bucks.

Whether a player improves or declines depends on his age and his CAREERPKG value. Players with a higher CAREERPKG value (such as A or B) have a greater chance of improving, and will likely improve to a much further extent. Players usually improve up until the age of 32, then begin to decline thereafter.

Where can I find out a player's CAREERPKG value?

It's a field in players.dbf, so you can look it up in a DBF editor such as DB Commander, or by using the NBA Live 2003 Toolkit.