After tepid economic news and a dim earnings outlook from Johnson & Johnson (NYSE:JNJ) stocks inched down with few big gainers.   Economic news was weak with existing home sales and the Chicago Fed National Activity Index falling short of expectations. Existing home sales for December reported by the National Association of Realtors fell 1.0% last month to 4.94 million units.   The nation's inventory of existing homes tanked 8.5% from November. The Chicago Fed National Activity Index reading of 0.02 was just high enough to maintain cautious optimism but it was not nearly as high as November's revised ...