A Florida couple came forward Wednesday to claim their share of last month’s world record $1.6 billion lottery jackpot, accepting a giant symbolic check but saying the experience has been “stressful.”David Kaltschmidt, 55, and Maureen Smith, 70, bought the winning ticket at a supermarket in the city of Melbourne Beach, where they live.The couple opted to receive a one-time payment of $328 million, before taxes, rather than $528 million divided into annual payments over 30 years.