IN DAYS OF AWE by Eric Goodman (Alfred A. Knopf : $20; 295 pp.). It's the pits for "Jewish Joe" Singer, major league New York baseball pitcher. He's fallen from national idol to bum, thrown out of baseball for failing to report a bribe attempt, deserted by his wife, reviled by the fans. To say that Joe's life takes a bizarre turn here is a Gargantuan understatement: Hiding out in a Hermosa Beach apartment, he enters into a daisy chain of sexual adventures, gets active in the gun- control movement, has one of his girlfriends killed by an irate husband and, finally, gets a bullet wound himself at an out-of-control gun meeting. Will Joe be reinstated by the baseball commissioner? Will he find happiness with still another girlfriend? The title, "In Days of Awe," refers to the period between Rosh Hashana and Yom Kippur, and it's suggestive of author Goodman's near-obsession with "Jewish Joe's" Jewishness--which doesn't much further the plot.