Yes he will kill his own child.

Prediction: Dennis is in love with Mac, he's forced to confront this during Mac's fake dating scheme in the finale (they make out or something), he chooses to leave to raise his kid because he always complains about his life/the gang's stagnation and it'll be an easy out, the gang helps Mac cope with his heartbreak by blowing up Dennis's car, Dennis kills his kid and comes back because what else is he gonna do, he's more upset about his car being blown up.

Mac and Dennis's relationship has always been gay but they don't acknowledge it because Mac was closeted and Dennis has always thought he would eventually do something with his life besides the bar/gang and Mac. Also it might mean growth for them to get together openly, and the show also does not allow the character's lives to improve, they must always get worse (though Mac's seemingly happier now that he's out and it would be interesting for this show to subvert the tropes that usually apply to gay characters where they die and/or are miserable and endure tragedy because they are gay by having this be the one thing that makes their lives better). Anyway, at the point that Dennis's only attempts at marriage and raising a kid have resulted in death/him murdering them, I think Dennis would finally be traumatized enough to resign himself to the fact that Mac has been and will always be his life partner and he'll never escape the gang.