How do I know what my dog's intentions are with my new kitten?

I just got a female kitten and we keep them separated. He's a terrier dog, so he has a prey drive, but he's acting calm around her, when we bring them close he sniffs her and lick her. However I don't like them getting too close because I'm afraid he's gonna bite her and try to eat her. He always tries to get to the kitten and when i bring her out he's fixated on her, jumping up and panting. I noticed his tongue sticks out and he starts drooling and licking his lips almost like she's a piece of meat, but he hasn't snapped at her yet or growled or barked or anything else that indicated he was being agressive, just very excited. So how do I know, without anyone getting hurt?