As a main-Jill guy I must say, Lana's story haven't got a hold on me yet, still pretty vague to me, the only emotional moment related to that that I can remember is Jill talking to MC after their first time that they hold hands and she talks about destiny (the reference to Lana here is the moon through the window). Also when they're at the lake and they talk about music and songs Lana liked, but it's not deep enough.
About the break ups, is one of my favorite emotional moments of the game, I like the dialogues, but as I said before, I rather see a bit more of conflict even if in some specific cases only, like Jill if you pick Bella, I'd like to see Sage sad and/or mad if you pick Jill over her.
About the throuple with Jill and Bella, I gonna say it again: would ruin Jill, makes absolutely no sense for her character, it would be pure porn-logic if she joins. The only threesome possible with Jill that I somehow see happening is with Bianca if the two of them decide to "party like old times" and get enough drunk for that. And IF that happens, I really hope for a regretful and ashamed Jill afterwards. Jill is too prude to be bi or experimental with sex, she found it hard to understand when MC slaps her butt during sex scene for god sake! How quickly something has to escale (yeah, bring the meme in) for that to make sense? The other possibility is her finding out somehow that Lana was bi and experimental in sex and trying to emule her big sis, but I would also see this as a long shot.