This doesn’t affect the argument. The author implies a comparison between the cost of treating early risk factors for mental disorders and the cost of treating more-fully-developed mental disorders, not between minor mental disorders and other, unrelated health problems.

This explains how the research program might be organized, not why it’s necessary to confirm the results of the existing research. It’s possible the previous research also included input from geneticists, neurologists, and behavioral scientists.

This makes concrete the author’s main assumption, that treating risk factors early is more cost-effective than treating full-blown disorders later. It justifies her advocacy for funding in order to develop those treatments.

This compares past funding with present funding, while the author compares present funding with future funding. She argues funding should increase to support the program described—she makes no claim about the present level of research funding relative to past levels.

This doesn’t affect the argument. There’s no indication that current care practices or the ones to be developed will cause mental disorders to disappear—only that they might help prevent those disorders from developing.