Well, great endurance! There are a number of threads on discourse about Error establishing a database connection. However, before even exploring those threads, I’d suggest you first wipe the server and rerun server.yml and deploy.yml. It’s very common that users who have had several failed iterations have their first successful run when they rebuild their server fresh.
If the fresh start approach doesn’t work, and looking through the threads about Error establishing a database connection doesn’t yield any insights, my next recommendation would be to see if you can get a vanilla trellis clone to work, making essentially no modifications other than your server IP and domain name. Compared to the long hard road of starting with a bunch of customizations and trying to get Trellis to work, it seems like a quick and easy road to get Trellis working with its defaults so that you know that your environment is ready and only then adding in customizations a piece at a time.