Jack's hands are twitching, aching to grab at that gorgeous, sore ass to perfectly displayed, but he controls himself because he does so love anticipation and there's so much more here to enjoy. He grins unashamedly at Spike when Spike glances at him, and when Ianto finally misses again he comes to the table with renewed purpose.
Down go all his remaining balls, followed by the black, and he grins triumphantly (and rather smugly, because that wasn't a bad result) and holds out his cue to Spike.