Number of columns is a fact about the section, not the page. If I were you, I would leave it as one column until I was 100% finished with that chapter, and then change the first page to 2-columns.

This works out OK really, since it is always recommended that you paginate last thing. Just add setting columns to the list of finishing chores.

There are other tools (linked textboxes, tables) to achieve multiple-columns, but none of them will work better in this situation, and in fact would be much harder to maintain.

I sure hope this helped.

I use Word to write books too. Styles make it so easy and fun.