It seems the manager the next morning did not understand the situation. (The manager may need to work on listening skills.)

The hotel owes you $100 USD under the Guaranteed Room Type guarantee. You did not to stay in a room with a King bed, despite your Guaranteed Bed reservation and your Platinum Premier Elite status.

The hotel also ought to give Rewards Points to you as an apology for the inconvenience and annoyance of forcing you to change rooms around 9 p.m., and subjecting you to a rude comment during the process, even if the comment was from a guest. I think most Marriotts would provide at least 5,000 points under such circumstances -- without being asked.