[Quoth]

Yes 1 means don't make any extra white space, i.e, 1 line widowed or orphaned is OK. Thus 4 means a minimum of 4. The default is usually 2 (if not set), as the compromise to having a line alone at the end or start of page (1) or loads of white space sometimes.

Hence 0 has no meaning.

The only 100% reliable method of keeping a heading with a paragraph is a page break before and the only 100% reliable way to do that is to start a new file.

Edit:
It's an illusion that it works in InDesign as it only 100% works in that for PDFs! It's a program for paper publishing fudged for fixed layout (which it works 100%) ebooks and for reflowable ebooks (for which it is atrocious).

Traditional publishers do paper first then ebooks. It is actually far better to not use InDesign at all at first and do epub2 without it! Then edit to epub3 for things that need it by hand. Then after content is proofed, do a version for paper either with InDesign or other tools.