what I basically want to do is this:
variable = \'whatever\'; fb.set({ variable : \"More Stuff\" });
So this will result in an entry that looks
Yes. The code is not working as expected because you are using object literal notation, which is the reason the it keeps the variable name as key, because that is how the notation works.
Solution
foo = {}; foo[variable] = 'more stuff'; fb.set(foo);