Interesting story here.
I'd be interested to know what trouble shooting you did on the day? I'm not rated on the 757/767 but are there circuit breakers for the inboard & outboard Ailerons? If there are, would it have been possible to pop either (not at the same time) the outboards or inboards CB's and thereby identifying and in turn isolating the troublesome Aileron? I would guess roll authority would not be as great if you had to isolate the outboard ailerons and only land with the remaining inboards controlling roll but that might of given you some reassurance and confidence in handling the aircraft for the remaining journey. Or allow you to divert urgently should you have needed too.
I'm sure all of this is in the QRH but i'd love to know how it was handled. I'm still learning so apologies if there's no logic with my reasoning or state the obvious.
Cheers,
Chilli.