Fry bacon. Crumble and set aside. Add flour to bacon fat, stirring with a wire whisk. Add broth and milk, stirring rapidly with whisk. Cook for about 10 minutes. In another pot, melt butter, add celery and onions. Cook briefly until vegetables are transparent. Add crawfish and smother for about 5 minutes. Add to milk mixture. Add corn, crabmeat, shrimp and seasoning. Continue simmering for about 10 minutes. If too thick, add more half & half. Add crumbled bacon.