I mean, no chance was Frank going to turn things around, but it's still a fairly awful concept to consider that both of these households are now set up in such a way that they will fall apart without Frank being a mess. And not just in a clever-writing or clever-concept way, but in a way that strikes to the heart of the matter, which is: Entire families are built around the addict, you make these compromises over decades in order to keep everybody alive and protected, you make them and their disease your fucking keystone, and that's sad and gross and everybody -- Lip, Fiona -- are constantly being tempted with a way out.
But as essential as each member of these families is, to the working of the overall mechanism, the fact is that if you pull Frank out of that Jenga party the whole thing will fall apart, because they have been covering for him for so long, taking care of him and each other, that they're bent into unimaginable arthritic shapes around him. Because Frank's drinking is the center of their lives, their lives collapse without it, which is the "dependence" in codependence. Which, it's fun to blame the victim and all, but if you look at it that way it's both strength and weakness at once. The inability to remember that life could be better, the inability to remember that surviving is not the same as living.
Which is why, by the time Frank's enlisted Carl and Debbie in his effort to "renovate" the shit out of their house, knocking holes in walls and turning the furniture upside down, Fiona and Lip agree he's done enough. "Last time he ripped up the floorboards, remember? Said he was gonna put in Saltillo tiles." Fiona had to screw a flooring contractor just to get it done. Debbie nods. "We have to kill the turtle. Daddy and Carl are up in the attic getting ready to cut a hole in the roof for a skylight. It's time to kill the turtle."
Of course, this mangles the turtle metaphor, but Lip knows what she means; because Debbie loves Frank more than anything both Lip and Fiona are hesitant about taking him away from her again, but it's Deb's world and we all just live in it, so when she says it's time for Real, they know she means it. "It'll hurt less now than if we wait two more weeks," it's decided, and they call Frank down from the attic. He comes running to save Debbie from the mouse she's yelling about, Lip hits him with the taser, and they pour vodka down his throat while he chokes and Carl screams.