Danene, ‘IP Accelerator’ is just a way to fasttrack Amazon Brand Registry where the trademark attorney is confident that a future trademark application will be successful. So fundamentally, it is a trademark application.
Trademark applications require you to demonstrate the use of the trademark (brand) in commerce. This means:
providing a photo showing the trademark in use, e.g. on your packaging,
confirming that customers have actually bought products with that trademark on it (and when that first occurred).
I recommend that you get your brand sorted out first (IP Accelerator can wait as it is a quick process if you have your brand in order.) So, make sure your packaging has the right brand name and change your Amazon listing to show the right brand name.
With your existing product and especially the 18000 units on the way, can you get those units rebranded? i.e. can you get rebranded packaging or even a sticky label with the brand put on them before they are sent to Amazon?