Need help with A-Level Further Maths Module choices

I did the same as you, in year 12. I did the M1 and M2 modules.
I say you should go for FP1/FP2, as you actually like pure and also the boundaries of the FP2 paper sort of cancel out the high boundaries of the FP1. In fact, last year, FP1/FP2 had the same boundaries as M1/M2 for Edexcel (262/300), which is reasonable.
I don't suggest picking M1 or FP1 alone, without M2/FP2, if you want low boundaries, as they always have the highest. In general, the X1/X2 combos will have lower boundaries than X1/Y1.
And, by the way, don't be discouraged by your mocks. I got a B in my mock and ended up with A*. At the same time, don't be too confident if you do get an A* in your mock. You're at inherent disadvantage by studying it all in such a short time.

I'm currently self-studying A-Level Further Maths to sit at the end of year 12 (due to some circumstances please don't question), I want to know which modules are the best option to pick. I really love pure but the high grade boundaries are scary, so I'd need a high level of mastery. The time i've got is september -> febuary (mocks, hopefully an A*) -> May (or whenever FM exams start) to sit the real exams