I do think he was nervous, in his boyish sort of way. Heath may look nervous when he fidgets, but I think Heath is nervous when he grimaces or freezes.

I agree. Heath's "tics" aren't from nervousness, just his crazy expressiveness. His nervousness probably shows more in his face, a stuffness.
Look at this, though, it's very funny -- he's actually sitting on his hands in this pic!
It doesn't seem like Jake was nervous in this show, but then, we can't know how he was feeling inside.
kathy