In no particular order, I think Phil still has feelings for Leanna, if for no other reason than he was, for a long time, comfortable with her presence and doesn't like change. Leanna also did stuff around the house and cooked him non-potato based food. But Phil also holds grudges, and hates to admit he messed up, which is why he memory holed Leanna. Unlike with Rambo/Howard, he can't really spin it with Leanna without straight up lying. And while Phil normally has no problem lying, I don't think he can think of a reasonable lie that also makes him look good. If he says Leanna was cheating, he looks bad for letting it happen/not finding out about it. Plus, I think he knows there's the possibility one of his paypigs would try to troll Leanna about it prompting Leanna to counter his claims. He learned that after trying to lie about Rambo, insisting that was about Rambo being overly greedy.
I pretty strongly disagree with the belief that Phil treats Khet like Leanna treated him. Leanna legitimately seemed to care about Phil and for whatever reason, wanted his attention. Phil will talk up Khet, sure, but that's more Phil bragging, since if he has such an amazing wife, it must mean it's because he's an equally amazing husband. He also wants to give the impression of a happy relationship to own the trolls or whatever. But other than that, it doesn't seem like he particularly cares about Khet. Her recent birthday is probably the best example of that I can give, where he made it all about himself by going to get fast food and then complaining nonstop about the infamous chicken sandwich. Maybe there's a world where they actually spend time off stream together and he gives her attention, but it's more likely they, at most, sit in the same room together while playing mobile games, sometimes with a YouTuber in the background. Based on some of Phil's recent day off talks, it seems likely Khet isn't waddling out of the gout fortress with him, while he and Leanna at least walked around the mall together.
I don't think Phil hates her or anything, he's probably indifferent. I think he's a little frustrated she doesn't do the same stuff Leanna does, but he still thinks of it as a win since he gets to pretend he has a trophy wife.