The thin smile is mostly Martel thinking of how hard Kalten hit him before he was interested in hearing reason; the things they said to each other first. He's not interested in rehashing the pettiness of that encounter with Sparhawk, though, so he lets the surprise stand without correcting it.

"Candice is my wife." Not legally, but he says it the way he'd say 'the sky is blue' or 'I love Sephrenia'. Like an inarguable fact.