Donte’ Stallworth began serving a 30-day jail sentence yesterday for killing a pedestrian while driving drunk in Florida, a punishment made possible by his cooperation with investigators and the desire of the victim’s family members to put the matter behind them. Stallworth, 28, also reached a confidential financial settlement with the family of 59-year-old Mario Reyes, a construction worker struck and killed early on March 14 by Stallworth, driving drunk in his black 2005 Bentley.