If you are picking subjects for their ease, I suggest neither chemistry nor French.
No, further maths is fine. Although I'm only mid way through FP1, so can't really speak for the entire course.
If you want to keep your options open to do science degrees, I'd take chemistry. If you want to take an economics or maths degree, I'd suggest FM. if you have truly no idea, I suggest you take 5 and drop one at a2 when you have more of an idea; you are perfectly capable of 5, with straight a*.
I left French out because if you want to go down the language route, one will suffice.