Floats are fixed point, just done in log space. The main change is that the designers dedicated a few bits to variable exponents, which introduces alignment and normalization steps before/after the operation. If you don't mix exponents, you can essentially treat it as identical to a lower precision fixed point system.
No, not even close. Scaling integers to mimic decimals under 32 and 64 bit can be much faster. And with 32 bit double numbers you can cover Plank numbers, so with 64 bit double numbers you can do any field.
