Yeah, I've always had an issue with Voight suddenly being a "good guy" despite planting coke in Casey's home, threatening to kill Casey, threatening to kill Casey's then girlfriend/fiancee Hallie, etc. All of this because Casey was honest in stating that Voight's son was driving drunk and caused a severe car wreck. Voight didn't want his son to go to jail, which may have helped sort his son out. Instead, he drops him off at the Army recruiting station and makes him join, yet his son still ends up dead later because of his involvement with drug dealers and other nefarious characters. Had he done the right thing from the beginning and let his son go to trial and possibly serve jail time, he might still be alive, though possibly in jail.
In any case, how can you redeem a guy who tried to completely destroy the life of a well respected fire fighter and who threatened to harm not just Casey but also his girlfriend/fiancee? The show acts like none of that ever happened and Voight faced pretty much no repercussions for it. What makes it even more absurd is that, after Hallie did die, Casey got involved with Gabby whose brother, Antonio, worked for Voight. This is another thing that bothers me about the whole Gabby/Casey relationship (Gabby herself bothers me immensely as does her constant manipulation of Casey) - why would Casey want anything to do with someone who had a family member that worked for Voight after all he did to him?
Regarding Louie, the saddest boy in the world, we got to hear him say one more word this episode which brings the season total up to three words, I think. He never smiles, never looks happy, etc. Again, I know he's been traumatized and whatnot, but Cindy has said that he has had a great time playing with her and Hermann's kids before.
As for bio-dad, given that he is a veteran and served our country, didn't know about Louie before, etc., under normal circumstances Gabby would have a hard time keeping Louie. It doesn't matter that she and Casey are now married as Gabby is the only one on the guardianship papers. Gabby thought that would give them an advantage over a single parent, but from a legal standpoint it doesn't work that way. In the real world, if the bio-dad just learned about the child (or even if he knew about him before he still has not signed away his parental rights), the custody of the child would go to him unless there were some really unusual circumstances. Technically, once the DNA test proved that he was Louie's father, Louie would have pretty much been turned over to him in short order (there would likely be a court hearing to rescind the guardianship as a formality) and if Gabby and Casey wanted to contest that, they could, but the child would likely be with the bio-dad while that happened, especially since, as I mentioned, the bio-dad never signed away his rights.