When post is too long, getting ERR_EMPTY_RESPONSE

So, this happened out of nowhere yesterday on my blog: https://ny-graffiti-artist-for-hire.com This is a very important site to me as I generate a lot of leads for jobs through it. I had a post in draft mode and when it exceeded a certain length, I am unable to Save The Draft and/or Publish it.

In Chrome, I get this error:
“Error code: ERR_EMPTY_RESPONSE”

In Firefox, I get this error:
“The connection was reset”

In Safari, I get this error:
“Safari can’t open the page.. because the server unexpectedly dropped the connection”

I can’t risk completely reinstalling this WordPress due to all the existing links out there. I tried uninstalling all plugins along w/ changing back to a standard theme but none of that seemed to work. The weird this is that I can easily create posts with a couple of words. Also, once this error happens, I can’t access my site at all for about 2-3 minutes and then it resolves itself.

Can someone please help as I can’t see to figure this one out?

Thanks!