How have you managed to accomplish self-hosted email? I tried similar in 2022 and found it damn near impossible without business static IP or a cloud provider.

I have access to a commercial (non-residential), fixed IP. You could also use an outgoing relay as a compromise, since presumably the issue you are facing is other servers rejecting email that you send from a disreputable IP. That being said, you really want a fixed IP as a matter of convenience if you are going to self-host anything.