I definitely think Tyrion and Sansa will see each other again, but in no way do I want them to be a couple. There is just too much bad blood between their families, and I want Sansa to either have a happy marriage, or none at all. Tyrion's "whore obsession" as you wisely put it is what drove me crazy.

Part of Jon's problem is that he tries to do the right thing in general, instead of trying to do the right thing for the watch. For example: his quasi-friendship with Stannis, the way he handled Alys Karstark, his perspective on the wildlings. The thing with Arya is like the ultimate temptation for him: she was the one person at Winterfell he felt the closest to.