Just to let you know, I was so frustrated with the setback of not being able to create ePub file which I could read at least on my laptop (which I was able to do before) that I checked it some more and eventually resolved the problem.
If I save the Hebrew file with Wordpad as text file with Unicode setting I'll get good ePub file which I can read on my laptop (same results when I save Unicode with Word, for that matter). It's not what I did before but what the heck - at least I can do it.
Back to Calibre - when I changed the metadata for the ePub file, either to Hebrew or English, it would do the same thing and save that file on my cellphone tghe same way, where Cool Reader will change the direction from RTL to LTR and render it unreadable (Nice Day will turn to Ecin Yad)
If you have a thought as to how to fix it I'll be grateful.