I had a quick nosey at the twitter account and it says Ross was well brought up, from a lovely family but he does have his moments. That makes me think he shows signs of a temper at times. I thought that perhaps they had met when he worked in the prison and when she worked as an ex police officer, maybe they started an affair then. Maybe on the day she went missing, she perhaps tried to end the affair which made him angry or he wanted to end the affair and she threatened to tell his wife so he killed her and dumped her body in to numerous bags. It says they were sealed so he obviously knew what he was doing - has he done this before? Or is just from what he's seen happens to evidence from where he used to work.
It's good that a woman in Barrhill spotted his car parked up so that suggests he has definitely buried her in the area. I would assume he has buried each bag in different areas around there to make it harder to be found or perhaps even removed her body parts from the bags before he buried them. Or maybe her body was not in those bags. Maybe those bags contained her clothes / the clothes he was wearing at the time / weapons he'd used to harm her etc. Maybe he has put rocks in to each bag to weigh them down and dumped them in some deep pools around the area.
What has this pal 12 miles away got to do with anything? Why would he apparently drop her dog off at home and Emma off at the pal's house. I wonder if he didn't work alone with dumping her body, if he got his pal from 12 miles away to help too. Do you know if they have spoken to him?
I can't imagine what the poor family must be going through. I also feel sorry for the poor dog who will be wondering where its owner has gone. I hope the search teams find her soon.