I really liked this story for the reasons you did, and I liked this Arthur hating feeling out of control and willing to consider the unthinkable to keep himself from dishonorable behavior and hurting his friend more. I too thought the ending was sort of flat, but the concept and execution till then was well done.

It would have been nice to see the bondage issue fleshed out a bit more though, as most reasons for bondage bother me a bit usually but this felt very natural. I do rather wonder why "must have sex" fics tend to have very strict ideas about sex meaning penetration and that only one of the pair is usually ever the catcher.

Ah well, as you say, small quibbles and perhaps just personal preference in the last bit.