Point 1 - Unless it suddenly comes back in any notable amount almost all of that is fluff and filler. Imagine if we had an interlude between Seasons 1 & 2 where we spent a day watching Nicole live her normal life (pick up her son, spend time outside of work with colleagues etc). Sure you learn more of the character but is it in any way relevant or benefiting the story in a way that couldn't be reached via conversations in a regular episode? That's the issue I have with Zoey and the Interlude in that even DPC seems to have acknowledged it's all superfluous given only a single choice actually feeds back into the main game and so far her adventure elsewhere has not had any relevancy.Point 1 - I got a lot more than just "she was his ex", and I like the backstory that you have for her, and that you see her emotions as well, via the interlude. The downside of course is that it's all together instead of spread throughout the previous 8 episodes like with the other girls, however, Zoey isn't one of the main girls who have their own path, and she has more to her story than probably all those others, with the probavbly exception of Quinn (and yes, I'm including Rio, Nicole, et al in this).
Point 2 - Respectfully disagree that Madame is less of a waste of time, and there's not really any evidence that she will play a bigger role, there's only fan theory based on a couple of isolated renders. She has less there than LiBrian has in the background, if you can to go down that route. But regarding the interlide, I wasn't about at the time, but I understand that was also done as something of a test (of the port from S1 to S2, I believe), so it wasn't just a case of having it to introduce Zoey.
Point 2 - Again, if Madame ends up having no role but the "Madame Scenes" where you instantly teleport to them to just watch a couple of animations, then it really is cheap content filler that are likely nothing more than animation tests.