1) My InDesign doc did include more than one page. Now removed and reduced down to 1 page.
2) I was able to check the "smooth scrolling" box in the (.article) export.
3) The entire page was scaled down to fit the vertical dimension (1536 x 4000 px). So that the page now only renders through the initial frame size. "Pinch to scale" makes the doc scale up, but only within the "scale to fit" dimensions that made the whole page fit vertically.
As a new user of this system, I am aware that I don't know everything about how to make it work, and there will be a learning process to get results – however, this seems like a simple process, and not being able to find a simple solution makes me really nervous about the purchase. I hope this can be resolved.