Wow.
Reading through the last page-worth of post seems to be an abundance of griping and kink shaming.
Frank isn't perfect. Not exactly a shock, yet is appears to be a major point of contention.
Considering that he's a 40-something who is in a rather nontraditional relationship, that he is attempting to come to terms with, while doing his best to ensure his family is happy, is this really that big of a surprise?
He encouraged his daughter to buy a sex toy for her to enjoy with her girlfriend. So what? I mean it is a harem story, and it's been fairly obvious that there will be relations between the girls. In one of the short extra stories Lil and Becca both have strapons going to town on Abby. While it isn't canon, it may very well be a preview of things to come.
In the vast majority of harem stories I've seen before, one commonality is that the group agrees that the one man is the only man for them. How much they participate with each other varies, though it is almost always a potential component. Since the harem tag has been there from the beginning, I'm not quite sure what people expected.
Doesn't matter to me if Abby is ever part of the harem. They can let her know what's going on, help her accept it, and she can join or not; I really don't care. Which is a little unusual since I'm rather fond of redheads. Far as I'm concerned, she can be in a side relationship with Lil forever, and just accept that the rest of them are with Frank and no other men.
To be blunt, I'd be fine with Frank eventually moving into a place with Becca, Lil, and Mei, letting Abby have her own place, and visiting Beth and Nessa on occasion.
Simply my opinion, not likely to be what happens, and that's perfectly fine. I'm not going to try and change the direction things are going, the relationship dynamics, or the story overall. Just going to go with it, and see where it ends up.
Enjoy the ride, or get off the train. No one forced you to buy a ticket.