He smiles and squeezes her hands.

I like making you smile too, sweetheart.

Since she's being so forthcoming, he'll show her how much he likes it when she smiles, or when she laughs, how he feels accomplished when he knows he's made her feel better when she's been feeling down.

Unfortunately the 'real' thing seems pretty unfeasible, since she can't really feel him when he's out of her head and there isn't a lot he can think of that will change that.