Posting for the first time, after spending a few hours reading through this forum. I have been fascinated by this case and so I'm very glad to find a place where it is discussed so thoroughly.
A few things: I have seen that Mona Earnest, among others, is one of the Martens relatives sharing photos of the Corbett children on FB. Unlike Molly and her mother, she is keeping her FB page open for comments, so the Corbett family and representatives are strenuously asking her to remove the public cover photo of herself and her husband (the same FBI uncle who has spoken on Molly's behalf and searched Jason's office after his death) with the children in front of a Christmas tree. Significantly, the photo was only shared late in 2015, but surely any Christmas photos with the kids would have been from 2014 or earlier? The caption of the photo says that Mona and her husband are with their "great-niece and great-nephew". Yesterday, I saw that someone from the Corbett family put an extremely legal post on the FB page about how the page was being investigated for child endangerment, and asking people to comment saying where they had seen other photos of the children. That post has now been removed, yet the Earnest family is leaving up other messages from the Corbett family. I think they are purposely taunting the Corbetts with this page so they can save any malicious messages. However, even the worst messages (while inappropriate) don't come close to what they are doing by violating the childrens' privacy and taunting a grieving family. So I don't see how this will work in the Martens' favour, but it seems like the only reason they are putting these photos out there and encouraging messages is to present the Corbetts as trolls.
Secondly, after reading through your evidence and speculation, I have come up with my own hypothesis - speculation only... I think we have a couple where the husband is undramatic and likes to smooth over any altercation, and a wife who is highly dramatic and confrontational, and she becomes especially frantic when she feels she's losing control. On Friday night, she taunts him once too often, so he quietly tweaks his travel plans. The next night after their casual get-together, they have some other confrontation and he announces that he's leaving for Ireland with the children - nothing to argue about any more, their marriage is over. He goes to bed at about 10pm, she's awake and fuming. She calls her parents and raises the alarm that something terrible has happened; they jump in the car and start the 4.5 hour journey to her place. She is still so angry and frantic that she goes to wherever the kids are staying and hauls them back home at 11pm. Once the kids are settled and asleep again, she is still pacing and fuming, alone in the house and getting angrier. Meanwhile Jason is still asleep until approximately 2am, when maybe he wakes up to go to the toilet. He's groggy and disoriented, not properly awake and she hears him and goes into the bedroom to attack him with the baseball bat. Once he falls to the floor, she keeps beating at him with the stone. By the time her parents arrive (approx 2.30 am), either she is still savagely attacking him or has only just stopped. Her parents take in the situation, and realize the attack is so savage, the only "excuse" could be self-defense, and it will sound better if they say the father did it. It takes them half an hour to get their story straight and ensure Jason is truly dead, and then the father calls the police. The mother disappears into a spare bedroom to lend credence to the idea that they were staying over.