Finally I´ve had a chance to see my epub-book in a couple of readers, I mean readers not in a computer. An iPad, even iPhone.
After that experience I will remove a number of footnotes. There was no precision in the jumping to and fro, rather it added an element of restlesness to the reading experience.
I will make parentheses of many footnotes and save them for the paper version, where it will be *I* who decide how a page looks, and where there ARE pages, not just screens.