Man that's rough, sorry it happened to you. The part that jumps out is calling it a "quick edit" from the client's side. That phrase is a huge red flag now in my book. It almost always means they don't see the work involved. Even trimming 30 seconds can mess with pacing and audio if you're not careful. Next time maybe shoot a quick email right away saying "happy to help with these new graphics, let me send a separate quote so we're clear." It stops the scope creep before it becomes a whole thing.