In 1956, Waco did have a minor league baseball team but they were the Waco Pirates, part of the Pittsburgh Pirates system.
Al says that one of the opposing pitcher's fast balls must have been 100 mph. The team was playing the last game of the minor league's season. There is no way the parent major league club would have left a 100 mph pitcher with pinpoint control on one one of their farm teams that late in the season.
The debris of the Bell X-2 falls down vertically in a straight line. If it had been destroyed at Mach 3, no matter how high, it would still have considerable forward momentum when it reached the ground, resulting in an elongated debris field rather than a 'heap'. It was probably dropped from a crane instead.
As Sam gets up after ejecting and parachuting to safety, the image of him is flipped, as evidenced by the backwards "U.S. AIR FORCE" label on his helmet.
The announcer says the funeral home has been serving Waco and the Hill Country...but Waco is not considered part of the Hill Country part of Texas. Advertisers would say the Heart of Texas or Central Texas area.
Al explains the theory of the Quantum Leap Project as Sam's lifetime is like a string with his birth at one end and his probable death at the other end. By tying the string together into a loop and crumpling it together, different time periods within Sam's lifetime can overlap and touch, making time travel possible. Despite this, Sam never leaps into the future beyond his trip back to 1999.
Al tell Sam he isn't allowed to reveal what year it is in the future. Moments later he tells Sam he can "wait 40 years" and he will get to the right year, revealing he is from 1996.