I have a question. The jury have to find him unanimously guilty to be found guilty. Do they have to find him unanimously not guilty to be not guilty? How does the ratio work if not all say guilty?
To my mind he did it, whether you want to accept all the pieces as evidence or only some it's still the only reasonable explanation for what happened to her - that she was killed and by her husband. I think the prosecution ran through the alternative options sufficiently to show they are implausible so you have to accept the only one that is. Sometimes I think the process of elimination can go to substantiating evidence and proving a finding in a circumstantial case, like trying to find the cause of death. By saying what it's not you can narrow right down to what it must be. Not everything leaves its own mark which is why elimination can work. Sometimes it's the lack of something that proves it. We use the process of elimination to find causes in other areas of life, this is no different.
The judge said murder is when you intended to kill or cause grievous bodily harm (that resulted in her death I guess). Manslaughter would be you accidentally caused it but didn't mean to, like hitting someone with a car while drink driving. You didn't mean to hurt them but are culpable. Here the fingernail marks and other scratches show she wasn't suddenly struck down with a single blow not meant to cause serious damage, she was really fighting back. You only fight back that hard if someone is seriously hurting you and for more than a few seconds. So there's intent to hurt her there, whether to kill or not, at minimum it meets the grievous bodily harm, so I'd find for murder rather than manslaughter. I don't think he planned this for weeks, I think something's happened where he's just lost it that night and acted out either rationally or irrationally.