This probably belongs in the oat forum.
Anyways, my advice to you is to push back the exam date. By the way, there is an opted practice oat test that is very similar to the actual oat, and that test seems to be the best gauge of scores especially for subjects like physics, so you might want to try that if you hadn't done so already. But what really concerns me is the 260 in Biology. There is a huge amount of material in Bio, so honestly with a test date just two weeks away, I think your best move would be to pay the reschedule fee (25 dollars if I remember correctly??) and have much more study time available.
It isn't as if December is too late per se to take the oat a second time if you needed to, but if you are certain you will get an awful score in two weeks, then pushing the first attempt back seems more logical.