Do you have your ptr record, aka your reverse DNS, this could cause deliverability issue if not set up properly. I don’t use Amazon SES, I run my own mail servers, so, if I am sending large emails, I do ip rotation, this way, you won’t have to worry when one IP gets blacklisted.
Have you tried warming up the list though? You might be sending too fast, so, you can either throttle the sending limit or use IP rotation.