Yes, it can be embedded, and it was set up that way at first. Two things stopped me. The page is taller than the itch embed window, so you end up scrolling inside a small frame while trying to read the tables. And the sheet currently holds one character at a time in browser storage, which is fine for a single PC but awkward the moment your party grows. You can export a character to a file and load another one back in, but swapping between three of them that way is a chore, and in an embed it would be worse.
Multiple characters is the thing I want to fix first, especially since a lot of solo play means running a whole party yourself. My own game went from one character to two within a session, so I ran into it straight away. Once the sheet handles several characters properly, a browser version makes much more sense and I will look at a layout that fits the embed.
Thanks for pushing on this, it is exactly the kind of thing I would not have spotted on my own.