I can only connect to the watch through espruino command line. Not through the web bluetooth client. So can't uninstall like normally, but with the client from the terminal I can install Js files, but I then need the bootloader files or the whole OS.
You'll need a more experienced user's answer then, I'm afraid. My suggestion had got me out of a similar problem when first using the watch, but it obviously doesn't always work.
Espruino is a JavaScript interpreter for low-power Microcontrollers. This site is both a support community for Espruino and a place to share what you are working on.
Can the watch still connect to the Banglejs apps page via bluetooth? If so, and the game is on the page, try uninstalling it from there.