I do believe that I will be sticking around now.
Kevin has been presented as black out drunk. A highly functional one, all things considered. So far just the right amount of situations have been presented in the first two episodes that you (I) could be to believe that, maybe, just maybe, he has an alter ego that is out there killing dogs for whatever reason to cope with his dysfunctional family life. You have: the other guy not having a name. There's no license plate on the DODGE Ram truck; it also happens to appear parked in his driveway. Kevin hasn't presented a proper description of the mystery man to the police department. He had a near wet dream with his daughter friend that lead to a encounter in the woods. The bagels go missing inexplicably.. Then bang, the guy is there on the front step and it's still a trippy, is this real or not moment, until the mystery man's presence is acknowledged by the girls and the beers are taken out of his hand. He talks to his dad, played by Scott Glenn, and no he doesn't have his shit together in the way he thinks he does. And the bagels did actually get stuck in the toaster.
So while we know he's not destined to go it alone, as his father and the imaginary voice in his head say, Kevin still isn't the most reliable protagonist moving forward. I haven't seen Justin Theroux "act" in more than a handful of movies, so color me surprised that he has the presence and skill to pull off this tightrope act so far in this series.