1) Are you sure you cannot change the font and and site theme without logging in? I just tested it and it works fine for me in private and incognito modes.
I purposely designed it so a lot of the settings are available via the quick action bar for non-logged in users.
If you have no-script active or have disabled javascript, then the only option would be to login to change them via the Settings page.
Otherwise, you should be able to toggle those easily via the quick action bar above the search results.
2) Definitely. I probably should have already done that.
3) I am still thinking on this. My plan was to soon remove it for upgraded accounts. There is no user-specific tracking, but by anonymously tracking clicks in general it helps with ranking and generating "popular" search results order.