From your Safari menu bar top of your screen click Safari > Preferences then select the Privacy tab.
Click: Remove All Website Data < removes cookies
Now open the Finder. From the Finder menu bar, (top of your screen), click Go > Go to Folder
Type this exactly as you see it here: ~/LIbrary/Caches/com.apple.Safari/Cache.db
Click Go the move the Cache.db file to the Trash.
Quit then relaunch Safari to test.
Just got to this again today. Doing the two steps you advised looks to have been partially successful. I still got the initial failure to load just like before. But at least this time, clicking the 'X' to stop loading produced an immediate "force reload" dialog (previously it would just produce a beachball, and I'd get to the "force reload" eventually after clicking stop again) -- and clicking the reload button in the dialog produced immediate success with the page loading successfully.
But it's still hardly functional! Wouldn't want to do this every day ... Does my partial success give you any further clues?