1) There's obviously not enough room on one "page" for the images. You need to resize the images so they fit (could also be the margin or the padding attributes that "push them over the top"). Your CSS can ensure that the image is automatically resized (I believe), but.....
2) As people increase the font-size, you're not going to be able to guarantee that the "two to four lines of text" stay on the same page as the image. Ever. Unless you make the text part of the image.
3) Don't use calibre's viewer to preview your ePubs.
4) Not really a Sigil question. It's not "creating" the blank page.
“Politics: A strife of interests masquerading as a contest of principles. The conduct of public affairs for private advantage.”