Formatting Large Project (Masters/Primary Text Help)

Hey there,

I've been using InDesign for a while, so I know most of the basics, but I've never formatted an entire novel until now. Here's what I'm doing. Please correct where I'm going wrong; this seems a frustratingly beginner mistake that I just can't figure out.

• I make my masters. I've set HEADING (for beginning-of-chapter pages) masters and NORMAL page masters to both use "primary text."
• When I PLACE the .doc novel, I hold SHIFT and drop it into a page that has the HEADING master. I make sure there's a NORMAL master following it so the document knows what to switch to. It works seemlessly. InDesign is smart enough to understand where to switch masters, and everything autofills.
• When I go into the master files and try to edit the dimensions of the text boxes, those edits don't carry over to the main pages. To my eyes, it seems like the placed text has disconnected itself from the masters. I'd like to be able to toy with the size of my text box in the master (basically, I'm testing different margins, especially for those opening chapter/heading pages) and have that carry over to all of the pages assigned to that master in the document. I cannot figure for the life of me why the pages aren't listening to changes made in the master.

Bonus question: when I import a document, those pesky tab indentations come in, and when I go to set my own indentation size, the tabs remain on top of my indentation setting, requiring me to manually delete every tab in the document at the beginning of each and every paragraph.

Thank you for your help!