On issue #1, if fl{<,<=,=,>=,>} were dyadic, that would be something to have to remember since the (srfi 143) and (scheme base) equivalents are all variadic.   It's trivial to write a macro to wrap a dyadic comparator into a variadic one, but everyone will end up cooking their own and we'll see this repeated in subtly different ways in shared code.    Ie. I prefer variadic semantics here.

A naming convention that makes a dyadic comparator clear would be a fair compromise.    $fl<, or fl<2, or something cleverer than I can come up with, just so it's obvious from the name so that on the rare occasion I need to use one of these functions transitively across many arguments, I'll know how to use it properly.    Ie.  I am not opposed to dyadic semantics if an alternative naming convention makes this obvious.

As for issue #2 - (fl+* vs. fl*+) -- I have no opinion one way or another.