By MARYCLAIRE DALE, Associated Press In a letter that surfaced after her 1994 murder, Nicole Brown Simpson detailed the fear and violence that framed her marriage to O.J. Simpson, the charismatic football star who became a TV pitchman. Simpson gave her "disgusted" looks with each pound she gained in her first pregnancy in 1988 and "beat the holy hell" out of her a year later, when the couple told an