Posed your question to ChatGPT and it came up with some things to try:
1700 pages + two-column layout + Hebrew (RTL) + David font + macros = maximum Word stress test.

Why It's So Slow
Let’s break it down:
1. David Font
Beautiful but old and heavy, not optimized for modern rendering.
Not well-suited for large documents — especially with complex layout and RTL text.
2. Two-Column Layout
Columns increase layout complexity.
With RTL, Word has to manage bidirectional flows inside and across columns, which adds rendering overhead.
3. Macros
If macros are modifying content, formatting, or layout dynamically, they may be running on every open, scroll, or edit.
That can drastically slow down responsiveness.
4. 1700 Pages
That’s enormous for Word. Word isn't built for ultra-large layout-rich documents.
It keeps a lot of layout information in memory, especially with columns and styles.

What You Can Do to Improve It

1. Temporarily Switch to a Lightweight Font
Try replacing David with Arial, Tahoma, or Segoe UI just while editing.
You can switch back to David before final formatting or printing.

2. Split the Document
Break the 1700-page document into smaller chunks (e.g., 300–500 pages each).
Use a master document or combine later into PDF.

3. Turn Off Features
Disable Auto-Formatting:
File > Options > Proofing > AutoCorrect Options > Uncheck everything you don’t need
Disable:
Track Changes
Spelling/Grammar check for Hebrew
File > Options > Advanced > "Update fields before printing", "Show text animation", etc.

4. Temporarily Disable Macros
See if the slowdown improves when macros aren’t running.
Save a copy > open with macros disabled.
If it’s faster, you may need to optimize the macro code.

5. Turn Off Live Layout
View tab > Switch to Draft view while editing.
File > Options > Advanced > Display > Enable "Use draft font in Draft and Outline views"

6. Move Off David Font If Possible
If this is for distribution or printing and you're tied to the David aesthetic:
Consider switching to David Libre, a modern open-source version optimized for digital use.
It retains the look but is lighter.