The “Text” editor was used to be called “HTML” which is probably the source of the references you find. (it is actually neither, but for sure it is not an HTML editor per-se).
As for your problems, this sounds more like a call to replace your keyboard, but assuming it is not an hardware issue you will need to deactivate plugins to find out which one is causing it (and switch themes to a vanilla theme if it will not be a plugin).