I’ve also noticed that if I play off the incognito page I get error 404 bad header saying the game is too large
Incognito mode is what is causing your save game issues, in other browsers it is called private browsing as I noted and other posters. Essentially if you want the game to play and retain saves then do not use incognito mode. The too large reference must be an internal bug or limitation for Safari.
If you use another browser and not safari then there are different settings or options here
If you really do not want your browser keeping data, then either
a) as suggested just load/save to file
or
b) install another browser, say FireFox or Chrome, and use it to play the game, and do not use it to browse the web (do not let it change to the default browser)