Page handing and numbering

I put up a post a couple of weeks ago but I'm still having trouble. I want page 1 to be a left hand page, but if I start numbering at 0, page 1 jumps to being a right hand page again. If I start the first page of music as a 2, then there is no problem.
I am editing a collection of 16th century pieces which will probably end up being about 100 sides of gt stave music. I have been working in three files: can I combine them without numbered blank pages? Or is it best to export them as pdfs, and then edit them as a whole?
What is the maximum size of a musescore file?