I think the reason his movement looks awkward is because Rafa is cautious and isn't comfortable putting weight on that knee yet. It doesn't necessarily mean he's still injured (could be of course, we don't know how it feels), but it does indicate he's been out for 7-8 months with a severe knee injury and isn't in prime condition yet.
Yeah. It's no secret how Nadal likes to be in a strict ruitine with things, and if he's thinking about movement all the time it's going to through him off from the norm.. Nothing to worry about yet in my opinion though, he showed slow improvements during the week.
As for the thread question, my answer is no. Nadal has lost on Clay before, and even thought his losses have came against top players, those top players still haven't gained the upper hand over Nadal on clay.