I've been trying to work out a timeline when he could have disposed of her. Would he have done it between 7:45am and 10:52am and used her vehicle? Or did he do it after he got back from placing her car near Clancy's, but before the daughter got home from school. Stebbins lets out at 2:40pm, so earliest she'd most likely be home would be around 3pm. That would give him more a bit more time, but also allows for evidence in his car.
Depending on when he did it, he has about a 3 to 4 hour window to drive wherever and get back. With that kind of time, he could have easily driven to Houston Woods, Caesar Creek, Buck Creek, or stayed closer to home like Huffman Dam area. Anywhere within a 75 minute or so drive is a possibility.
I think it's possible that he killed her wherever he put her after incapacitating her at home.
I can't even begin to imagine. I certainly hope the daughter has a good set of strong friends because she's going to need them. Having a father be a suspect in the disappearance and murder of your mom is hard enough, but having everyone know about it and still having to go through your day at school is going to be rough. Teenagers are cruel and this is something that they'll run with.