*Futures up: S&P 7.5 pts, Dow 57 pts, Nasdaq 7.75 pts. NEW YORK, March 6- Wall Street was set to drive the rally further on Wednesday, the day after the Dow set a new record, as hiring by companies rose strongly last month. "I think this is a happiness hangover," said Kim Forrest, senior equity research analyst at Fort Pitt Capital Group in Pittsburgh.