My vote is also for retaking the DAT. It will be much less stressful and significantly cheaper than doing an entire extra degree. Don't underestimate the work it takes to get a 3.8+ in grad school. If you did the masters and messed up badly (low 3), you would be in a very deep hole.
If you want to cover all of your bases, I'd retake the DAT and then take a few upper-division courses this fall (post-bacc) to show your continued success in science courses. Do that, apply broadly and intelligently, and you should be good.