OT: I'm still searching for a tool/scriptlet to load my whole history off youtube. The API commands allow only the last n (I think it where 50) entries to fetch, and the interface of youtube is even worse.
Write a JS snippet that will press the "Load more" button every 2s on the web interface. Let it run for a lot of time, on Chrome DevTools, then scrape the page with Javascript. Seems relatively easy.
I did something like this with firefox, but after a while firefox was using so much RAM, it took him 10-20 sec. for a single request - I gathered ~40000 history entries with this technique. Perhaps Chrome DevTools will do a better job - I'll try.
Ok, you have too many history entries. That will be a problem everywhere. Perhaps removing CSS, media and images from the DOM will reduce memory consumption and get your farther?