Dreamweaver is slow to refresh

[MLandis]

I have a page that I started 10+ years ago that I keep adding to. It's got a lot of nested tables, is a little over 1MB in size (very few linked images) and has 19,220+ lines of html code. For a few years now, the file will get really slow to refresh. I'll click to place my cursor somewhere and it seems locked up and I get the white overlay and the window says "Not Responding." 
I'm using CC19 version (because the new paste in cc20 doesn't keep my line breaks). 
I've reset my preferences. I've cleared my cache. I'm using the most recent cc19 version.
There are no errors in my code.
IS THERE ANY WAY TO FIX HOW SLOOOOOOOOOW THIS PAGE IS?

[Nancy OShea]

Divide and conquer.  Get rid of 19,000 lines of code. 

Split your one page site up into a multi-page website.

Run performance tests to ensure your online web pages don't take too long to load.

https://gtmetrix.com/

[BenPleysier]

I get very nervous when an HTML document surpasses 500 lines of code.

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