The hundreds of relays is how nostr is supposed to be. Those are relays from all the people you are following. You are getting posts directly from their relays.

The posts are probably followed hashtags from other clients in the past. We now used the same list Primal and others use, if you signed up there, you could have added them to the list and will show up on Amethyst. You will need to unfollow them to work.

I am releasing a few bugfixes soon, including a bug on unfollowing hashtags.