Dexter is lying about where he hid the body - maybe the wrong grave / cemetery, maybe he just dumped the body at sea per his usual methods. There was no internal dialogue at that point, which to me suggests that we're meant to believe him for now, and that the grave will be exhumed sooner or later.
One or both of the tree surgeons knows more than he's saying, or is the killer.
The shirt will be useful to Dexter sooner or later when he needs to cover his tracks.
The DA is covering something up in the wrongful conviction - maybe one of his brothers was the killer.
I think there's something fishy about the DA's arrival at Freebo's hiding place, but I need to rewatch the episode to check.
The pedophile put pictures of Aster on line.
Deb will end up in bed with the singer.
Be interesting to see how much of this becomes plot points in later episodes.