I agree with much of the contributions above and so don’t really have much more to add. Getting into Oxbridge is tough but as with other top institutions, there’s always a degree of unpredictability in the admissions process - each year, some you expect will get in don’t and others surprise on the positive side. This is because much rides on the Oxbridge exams (in OP’s case, the TSA) and interviews so the “paper” qualifications simply get applicants through the first gate.
Compared to the highly skewed Oxbridge applicant pools, OP’s record probably sits in the lower half (overall it is highly impressive). For example, two of my D’s friends at Oxford who took US standardized tests scored 1580 (or 1590) on the SAT and 36 on the ACT (my D had similar performance in a single sitting). On high stakes exams (A level and IB), D and her friends have perfect or near perfect records (my sense is that these exams are more challenging than APs). I am sharing this not to dissuade OP but to give him/her a realistic picture of the competition.
One aspect that OP might wish to consider seriously is whether he/she would enjoy studying a single subject for 3-4 years, particularly if biology is chosen, as the academic experience at Oxbridge is incredibly intense.