Unless Miss Motive had been in the Coleman home recently, there would be the problem of the ex knowing about where the cameras were located, the location of the dvr, and the layout of the home. Then you have the problems of no forced entry into the home, the limited time frame with the phone ringing constantly, no strange vehicle, no stranger seen coming or going, and several other things. The threats are don't fit it being the ex either, like Wrinkles mentioned.
No. Not buying that Miss Motive or her ex had anything to do with carrying out these murders. Nothing points to the either one of them. LE would have already verified their alibis.
It would be nice if LE would tell us who they had cleared.