Even though testosterone decreases as men age, it is still present. Weight lifting will help you gain muscle mass, which burns calories more efficiently than other tissue types (like fat). That being said, if you increase muscle mass without doing aerobic exercise you'll maintain or even increase your weight. Lots of good advice here about combining cardio with dietary changes.
Mason, your Y pool workouts are a good start. I would advise adding stationary bike (20-30 mins/day) or treadmill or eliptical to your routine. Try to limit your carb intake to no more than the equivalent of 3 slices of whole wheat bread, or one medium baked potato, or a cup or less of whole wheat pasta. Fill up on veggies, the less cooked the better -- they give you a feeling of fullness while working out your digestive tract which prolongs the full feeling. The advice from JD about yogurt for the sweet dessert is a good one. I would also try to limit your protein intake to no more than the equivalent of six oz of meat/chicken/fish per day if possible. Water, drinks lots and lots of water -- 64 ounces a day or more.