It's casual and crowded, with red gingham tablecloths and lots of noise, but Daddy Jack's is an institution. The chowder is hearty and the grilled fish always fresh, though sometimes pricey. But there's one thing tightwad gourmands can always count on. For years, every Monday through Wednesday, Daddy Jack's has served up Lobster Madness for dinner: $12.95 gets you lobster (tail and one claw), baked potato, a veggie and fresh sourdough bread. Don't even think about going without reservations, and you better arrive before 7:30 p.m. or the cheap crustaceans may all be gone. Then you'll just have to splurge on the jumbo lobster tail. Strap on your bib, grab a fork and guard your dish of melted butter from poachers.