For a long while, he keeps 'silent', just offering the Doctor his support and 'grounding' like the Doctor had said. He squeezes the Doctor's hand with his, trying to just concentrate on that and not Jenny's suffering. It's hard not to; he can definitely empathize. This is about helping her, though. The Doctor basically said to just help him with it... but he can do more, can't he?
He offers Jenny his free hand and a gentler smile than his normal one. "Hey there. Another strong arm to help haul you up while your dad's talking you through."