I like to theorize.
Gerard was bitten by Peter Hale sometime in the past. His medication is some sort of werewolf suppression cocktail. He dropped his interest in what was up with Lydia because he figured out her connection to Peter and he wanted her to bring him back to life. Killing the alpha who bit you can cure you and Gerard will use Jackson to restrain Peter. His new war on werewolves is less about Kate’s death and more about keeping Chris and Allison distracted. Also because he really likes killing werewolves. Allison’s decent into the dark-side will be slowed when she finds out grandpa basically let her mom die even tho there was another way. I think Mama Argent is truly most sincerely dead (but you never know.) And maybe Chris kills his father once he figures out the truth, that’s got Greek tragedy written all over it.