You're welcome, Isaac.

Concerning the "differences in health outcomes", you need to think the other way around: the standards are developed based on epidemiological data correlating BP cutoffs with cardiovascular and other disease events. The idea is to find an optimal point at which as many cases as possible can be prevented, while treating as few people as possible who wouldn't need treatment. That's a statistical balancing act. Health organisations like to err on the side of caution, which is why the NNT is relatively high.

Once-a-week BP measurement might be a little too infrequent to get a reliable picture of average and trend. I recommend my clients to take it daily, ideally in the morning before getting up. The objective is to always measure under the same conditions, since BP is a biomarker with a high variability.