To be honest I agree. I now think any guilty looking expressions in interviews were because it wouldn't appear to have been that happy a relationship, or maybe he feels or knows he might have driven her to do whatever, if there was no 3rd party involved. Or maybe it's just he'd be relieved if she were dead or remained missing but he has to try to look like the loving partner because that's "what is done" in these circumstances. They may have been as bad as each other, in a toxic relationship, or maybe she was more innocent than him, who knows. But after finding out about his TikTok and Pinterest, you're right, he's far too thick to be a competent murderer.