You're really mixing two different things. You're saying that he hasn't really gotten it done, because if you remove luck, etc he's been slightly below average. Regardless of how he's done it (it can be pure luck), the actual results (run prevention) have been above average, which is "getting it done". That doesn't mean we can expect him to continue to do so going forward (advanced stats suggest not, at least until he curbs the walk rate). It also doesn't mean that he's outpitched his peers thus far in a neutral context.
As for future health, I don't believe the sinker should cause him any additional issues, nor the curve. It seems health issues tend to come more from the cutter / slider.