Overkill. Very common to have a little water damage around toilet. Patch it and move on. I would not have let the first knife go into drywall. Turned this into a huge inconvenient PITA
Agree. I think, you were taken advantaged of. Been in similar situation.
Plumber's use the "scare" technique, to get your approval.
My best advice for future issues. Sleep on it for a couple of days. And
ask for advice. This forum, friends, etc. To avoid being taken to the cleaners.
Good luck. I think you said, your toilet on 1st floor, concrete. So damage
should have been minimal.