JMJ
I don't mind that Frank seems "out of character" because you're right that it's plausible that he'd be different when alone with Kristen. But I don't know about Kristen. We've seen her alone with Gary in one episode and it was implied that she was alone with David in another; she comes across as flirty and not really serious about going steady with one guy. I think your premise has real potential, but that Kristen needs more fleshing out.

Also, I don't really think having their thoughts in italics is really necessary. I'd say your dialogue and descriptions are strong enough for the subtext to be clear. )

Will you be continuing this? It would be interesting to see how you make it fit other episodes, especially since Frank would have more to be jealous about than Kristen.

great story.