I don't know about it changing your characters, but you can search for a string verbatim by pressing ctrl-r at the start of the search pattern, like this:

  /<ctrl-r>~?

Exodus (https://github.com/intoli/exodus) used to be good for this but is giving me a Python error these days.

Try https://addons.mozilla.org/en-GB/firefox/addon/feed-preview/

Open With, although it's no longer maintained: https://addons.mozilla.org/en-GB/firefox/addon/open-with/

Reminded me of Osmos: https://www.osmos-game.com/