Jack? Definitely an ENTP if I've ever seen one. It's true that he shows a lot of Fe, but his Ne and Ti are definitely stronger. He's the typical enthusiastic, excitable, innovative scientist-inventor, who occasionally goes almost frenzy, which is virtually the definition of the ENTP archetype. If he was Fe dominant, he would know better how to use this function, but he pretty much screws up everything regarding it. Also, he's not a J. Every 'mad scientist' has lots of plans, that's what Ne is for; the J indicates ability to follow them through, but Jack just improvises most of the time and the 'success' of his actions is evident. Sally is probably an INFJ - she's the feeling judger who's keeping him from 'succumbing to the dark side' of Ne-Ti.
I'm sure about their types also because I've been writing a novel where the hero coincidentally ended up being an ENTP and the heroine an INFJ (way before I knew about MBTI); the story has a lot of parallel situations and the chemistry between the characters is absolutely the same.
To be honest, sometimes it seems to me that people here theorize about MBTI too much and miss the big picture. Fictional characters are usually just 'types' (and even that only if they're well written), and it's not worth typing them by some minor details of their character. The big picture is everything here.