The Terrasoul Superfoods Raw Organic Cacao Powder lists the dose as 1 tsp (3 grams), whereas the Earth Echo Cacao Bliss – Ceremonial Grade Organic Raw Cacao Powder lists the dose as 2.5 teaspoons (8 grams). What dose of the Terrasoul powder would be effective for imparting the desired anti-aging benefits from promoting stem cells, etc?

This is simply a matter of personal choice. There is no arbitrary amount essential to get a benefit, but what happens will be in proportion to dose. So a larger ingestion of 8 g will have a greater series of beneficial effects that will a 3 g intake. The latter is not inconsequential, but we would say in wanting to counter the challenges faced by physical beings and their all-too-short lifetimes, there is not a lot of time to waste, especially when an older person is wanting to reverse effects of aging already well underway in undermining their well-being and likely longevity.