IF Honey was killed by Barry elsewhere and moved to the pool railings area already dead, I think it would be difficult for him to even get her into a seated position, let alone to remain in a seated position and lean her forwards and hold steady the belt loop with one hand so that it goes under her chin, being that she would be an uncooperative dead weight.
The moving part could be achieved by dragging but it's the raising of her upper body from a lying position to seated and then the positioning that raises my incredulity with a 75 year old noted to be lethargic and Honey not being a slight or petite lady.
FWIW my doubts aren't so much about whether husbands kill their wives before committing suicide in the most unexpected of cases, it's that it's an awful lot of trouble to go to to stage it as that manner of suicide, given that her death was obviously premeditated. Honey died of ligature neck compression, not by hands. Why would she have been taken surprise like that, if she was dressed in a jacket, so not asleep. I still think it had something to do with arriving home in her car. Plus there must have been evidence she died elsewhere IF the early leaks were true, so he didn't even bother to clear up that scene of death.
I am wondering more if Honey didn't die elsewhere (not substantiated by 'sources' I know) so much as having been injured or incapacitated elsewhere, meaning that she was unconscious and then died by neck compression by the belt. That still doesn't explain how he could have managed that maneuvering or why he would do it. He was known for his intelligence and would have known his suicide set up would be easily discovered by investigators.
It seems this person, whether it was Barry or a third person, mucked up the double suicide staging. If it was Barry that makes no sense because he had time to clean up and because it would have mattered to him. I tend to think currently that if everything else was achieved without a mistake, no traces, this was someone who was covered head to toe including gloves and a mask, not leaving a hair, a fingerprint or touch DNA at the scene. If that is the case, imagine Honey did somehow leave evidence she was attacked somewhere else, be that blood, urine or feces. This hit man isn't going to touch it. That would leave a trail of trace evidence on everything they came into contact with as they made their get away. He could drag Honey with hands under her armpits without stepping in anything.
How to explain Barry's apparent suicide? He is forced to comply, can't see a way out, perhaps thinks even that he is saving Honey by complying, if he knows she has only been injured and there is a chance she won't also be killed.