In regard to your first question, generally speaking, the view of the Word page will automatically jump to 2 side-by-side pages at approximately 75%. Once you get much larger than that, it should revert to showing one page at a time, with the next page below it. Check your “Two Pages” icon (in the Ribbon) to see if it is enabled. If it is, uncheck it.
In regard to your second question, there are several possible explanations. The new document will open up in the format of the Normal template, so check the formatting section to make sure that your Normal template settings are what you want for your new docs, and don’t forget to click the link at the bottom of the formatting screen that says to apply the settings to either:
1. Only this document, or
2. New documents based on this template
If you wish to have each new doc to have different margins, you have to set them for each such document:
Click the Start orb, go into Word Options, Advanced and check:
1. Keep track of formatting.
2. Choose your Default paragraph style.
3. And at the very bottom of the screen, at the link entitled: Compatibility options for: select either This Document (Document’s Title) or All New Documents.