I totally thought the scene where Emily/Fiona died would snap Frank into reality. we all know he won't follow a doctor's orders.
I guess it just proved that if you (delirium) daughter dying in front of you can't make you turn over a new leaf, nothing can.

I think maybe the reason they kept the Matt/Debbie bit was because he showed up at their house and was acting friendly, so they wanted to remind viewers that he was no longer avoiding Debbie. It's the only half-plausible scenario, to me.
As for the lack of touching on the incest … Justification for Frank taking up…

Jimmy's wife's dad didn't care that he was sleeping with Fiona, he made some comment about him being allowed to have Fiona on the side as long as he took care of Estefania. He only cared that Jimmy was around when immigration showed up. He was really just pissed about his daughter nearly getting deported — admittedly…

I have a lot of thoughts about this finale, probably because this season was such a departure from the shenanigans we're used to seeing.