A lot of the above is nonsense; Cambridge don't really care about GCSEs, for starters. While many of their successful applicants do have strong GCSE results, this isn't due to them selecting for those with strong GCSE results, it's because those who did well at GCSE normally do well at A-level. You can also do well at A-level even if you do poorly in GCSEs, and as the college ATs have said time and again, it's your A-level performance they care about (in fact all the ATs that currently have reps on here have stated at one time or another that they have never rejected a candidate solely on the basis of GCSEs). Although the A* doesn't necessarily have to be in English, they may well specify it be in English when they make their offer. That is at the offering college's discretion, and they do sometimes require the A*(s) be in specific subjects to try and see candidates stretch themselves to that higher level of achievement (this might be more common for STEM subjects though).
You're only halfway through year 12 (well, a bit less than that actually) so there's certainly time to improve. Whether that's enough time to improve enough to get the necessary predicted grades, perhaps not - but A*AA or above is certainly achievable in that time if you focus on your studies, and then you could apply in a gap year (which would give you the chance to do more wider reading as well). An EPQ seems neither here nor there; if you have some specific topic you want to explore more outside the confines of your other subjects, by all means to an EPQ to facilitate that, but it's not likely going to make or break an application to Cambridge or elsewhere.
Also, consider the alternative - is there any point in not trying for Cambridge? At most it's 1/5 choices, and you can only accept at most two offers anyway. It's certainly possible to construct a set of universities to apply to including Cambridge which near enough guarantee the chances of at least one offer, if not more.