In that case the wiki notes on the
Fire TV (wiki) should be a second port of call, and the pages from it.
If just doing an add-on uninstall doesn't work, then if you have access to the file system via a suitable file manager, just go in with Kodi not running and delete your .kodi folder (it's one level up from your
userdata folder (wiki) - follow that link for a table showing where it can be found). Note that the .kodi folder is a hidden folder, you may need to enable hidden file/folder viewing to see it.
When you restart Kodi you should find it completely reset to a first time use status with nothing installed. Note this will remove everything and reset Kodi back to a fresh vanilla install.
Alternatively you can just delete selected folders from the addons folder (you can find that in the .kodi folder at the same level as the userdata one, each add-on will have its own sub-folder within it) and also the corresponding sub-folder in the addon_data folder you can find within userdata. That should just remove the selected add-ons, but it a little more tricky to do.
Lastly you may want to consider just uninstalling Helix and side-loading Jarvis (or Isengard) unless there's a specific reason to stay on the older version. Details of doing that are in the link at the start of this post (or directly -
HOW-TO:Install Kodi on Fire TV (wiki)).