Sprinkle tilapia with salt and pepper. Place in a 13x9 inch baking dish coated with nonstick cooking spray; set aside.
In a small nonstick skillet coated with nonstick cooking spray, cook the celery, onion, and garlic in 2 teaspoons butter until tender. Stir in flour and thyme until blended. Gradually whisk in milk. Bring to a boil; cook and stir for 1-2 minutes or until thickened. Stir in the lemon juice, Worcestershire sauce and hot pepper sauce.
Remove from heat; stir in mayonnaise until blended. Stir in crab and 3 tablespoons bread crumbs. Spoon onto fillets. Toss remaining bread crumbs and butter; sprinkle over crab mixture.
Cover and bake at 350 for 18 minutes. Uncover and bake 5-10 minutes longer or until fish flakes easily with a fork.