Having read the study now: DASH-sodium barely indicates anything about sodium independently. It looks at three biomarkers which _correlate_ with cardiovascular disease, and finds that reducing sodium from high to low levels for four weeks reduced one of those biomarkers by 19%, _increased_ another biomarker by 9%, and didn't change the third. You could say that this suggests higher sodium increases cardiovascular disease risk but that seems like a stretch when if you'd picked a slightly different set of CVD-correlated biomarkers you would have got exactly the opposite result.
Even if the results had been more convincing, the methods are not - it's an extremely short term study and looks only at correlative biomarkers and not at actual health outcomes. There's no meaningful way to quantify the impact based on this.
The potassium study is indeed interesting. It shows among people who already have CVD, a reduced risk of death of 12%. I think it's pretty well known that modern diets have a significant electrolyte imbalance, i.e. not enough potassium per sodium. I do supplement potassium for this reason sometimes and recommend it, though I'd prefer to just have a ton of natural nutrient dense food available and not feel like I need to. So we're in agreement on that one. That said I don't take that study to strongly show that sodium is a primary driver of CVD - it could just as easily be interpreted that the lack of potassium due to lack of real natural food is a cause of CVD (potassium being mostly in nutrient dense greens, and grass fed meat (i.e. animals that ate more natural diets i.e. greens)).
So, thank you - this helps my understanding of the whole topic - not that I know the answers, but it does make me more curious about sodium/potassium electrolyte imbalance being a factor in CVD. Ideally this would be fixed with a healthier diet but it can be hard/expensive to get enough nutrient dense foods.
Edit: oops - I missed the TOHP study - but that's one where they don't isolate sodium: > The active intervention, described in detail elsewhere,22 involved dietary and behavioural counselling on how to identify sodium in the diet, self monitor intake, and select or prepare lower sodium foods and condiments suited to personal preferences. Individual and weekly group counselling sessions were provided during the first three months, with additional counselling and support less frequently for the remainder of follow-up.