I've seen her statement reported in various different ways by various different media outlets. That's why I take it with a pinch of salt. When it was first printed it was more a comment that they were hoping to reunite soon but were not sure when. It then appeared to be embellished with extra details added on. Therefore I personally have never been sure exactly which part was factual and which was embroidered by media.
The police comments about their relationship not being what it seemed or something were interesting but they were never really elaborated on so it makes it easy to fill in the blanks, potentially erroneously (or not, of course).
I'm not sure if their actual relationship was dysfunctional. From the posts I read at the time (their blog and her Facebook) I thought it seemed more that they had both been through a lot and were struggling to find happiness in themselves rather than within the relationship itself. I got the impression that whilst being in each other's company 24/7 could be challenging (it would be for anyone), that they enjoyed individual pursuits to give them the space needed. I view that as being a sensible and mature thing to do, not something that's a red flag. I feel a lot of things he says/does could be percieved in two ways, one negative, one more positive.
However even if they were likely to separate, I find the leap from him talking over her in a video meaning he's absolutely being controlling in their relationship and had bugged her phone and controlled what she ate, a stretch too far. There is no solid evidence for that at all.
There's a lot of assumptions and judgements being made about someone from what is realistically a very limited amount of knowledge (although to be fair the same could be said for the majority of cases similar to this). He's spent the best part of a year not knowing what happened to his long term partner but realising she was probably dead. Even if things had been difficult between them it's still an enormous loss for someone to cope with. I think some of the way he has conducted himself could be considered unusual but he's likely to not really be thinking straight.
It is of course only my opinion