One can see, by both instances in the book, previously quoted, that Jake didn't get out of class until 10:00 AM, the same time his wife left for her appointment and that he picked up his sister-in-law at 8:00 AM. Assuming it's a one hour class and he picks the S-I-L up, as usual, at 8:00 AM, if it takes an hour to get there, it also takes an hour to get back home so it would be eleven before he got home. The book says well before noon which I take as 11:30 AMish tops. (Would Mary Ann have waited at the mall an hour/hour and a half?)
Assuming that grade school gets out at 3:00 PM, that makes only a 4 hour window of opportunity in which Jake goes to the mall, incapacitates his wife, throws her in the trunk (where her wig falls off), drives through city traffic and then 170km/105mi at 55mph for 1.91 hours to the Ft. Assinibone area, dumps her body off in one location, drives to another location and disposes of her clothes off the side of the road, drives to another location, gets rid of her suitcase, drives to yet another location, gets rid of real estate papers, then makes the 170km/105mi 1.91 hour trip back to Edmonton doing 55mph, drives through city traffic and gets home in time to pick his kids up from school, or meet them at home, at 3:00 pm.
I highly doubt it. If the statement by the woman about the victim and killer being seen out at the acreage is true, that would make the above scenario that much more incredible.
Considering that a serial killer didn't get her, which is probably what happened, I'd say the next best scenario was she was taking business away from another (jealous) realtor who was losing business because of her success. That's why the paperwork was hidden, in two locations, no less, and not brought back. The killer thought there would be something in the papers implicating him in the crime and he was making sure there was no evidence being brought back. That's the angle I'd pursue, second to a serial killer scenario.
As far as Jake marrying so soon after the murder, he came to grips with reality and moved on with his life.