Constant notifications for activation key

someone is trying to hack your account.

not sure you can do anything to stop it.

eventually they will give up...

Try using facebook through another alternative.

You can use a browser like Brave, or Basilisk + Firefox add-ons + Noscript
You could have a device just for Facebook
You could use an official app for whatever OS you want.

Another thing is to change you passwords and then even after that you should contact Facebook and ask them ( on the phone ) could you inform me of any access from other locations. Deviant Art has that listed the logins attempts you make