You're giving statistics that back up your point of view. But in this case, they don't exactly apply. We have a singular account of the last sighting of Barbara given by a person who is "statistically" most likely responsible for her disappearance.
SAR spent 10 days searching and were unable to find her. So she didn't have some sort of medical malady or mishap in a national park. LE has said there is no evidence of an abduction, they don't feel that is a possibility. So realistically what are we left with?
IMO, either Robert disappeared her or she arranged her own. I'll be open to more possibilities if more facts are made known. But it appears LE is using super glue instead of chapstick.
Your using a flawed argument, too. The most likely person to have murdered her is her husband based on statistics. We don't know that she was murdered, though. You're making that assumption then claiming statistics back you up.
The most likely reason she is dead would be due to a medical event. We don't know if she is dead, though.
The most likely reason for her to be missing is probably either choice or a car accident. That doesn't seem to fit in this instance.
Statistics don't mean anything here when they come after unproven assumptions.