I hesitate to say that Chrome leaks memory because of what you're seeing. Webpages have exploded in size over the years (both with high dpi images, css, and javascript). I'm not sure I have quite as many tabs as you, but I generally work the same way (window per topic, tens of tabs per window).

Would a plugin like The Great Suspender fix your problem? I really liked that you could collapse a page of tabs into a collection of bookmarks and open a new page of those tabs just as easily.