I don't rule out a side dish, as we're calling it tonight.
We don't have any evidence so far of another woman, but of course it's possible.
I think he didn't want to deal with her AT ALL anymore - no shared custody, no lingering engagement, no "when are you going to move out of your mom's place" conversation, no Kelsey.
I realize most people would simply break up. But that's not what happened. She's dead, and from the charges, he planned for murder.
He killed her, imo, and I think it was out of disinterest in her completely. She didn't fit in (I'm guessing), she wasn't leaving and would never completely leave even if they broke up - and he wanted to be rid of her.
So, he got rid of her and didn't even bother faking concern.
jmo