I dunno why you say FreeCAD is bad. When I got my 3d printer I picked it because I knew fusion would rug pull eventually, and fusion doesn’t run on Linux without jumping through a bunch of hoops.
It takes a bit to learn, just like any app. But it’s just as powerful. I really like the spreadsheet usage in FreeCAD to keep all my dimensions in one place.
I have a feeling you don’t quite understand what Docker is doing for you and how it works. I suggest looking for an intro to Docker and understand the basics around Docker volumes and networking in docker before trying to orchestrate a complex set of software in Docker.
Don’t give up! I was you about 6 years ago. I’m on my 3rd server setup now, and I’ve gone from where you are now, to being able to script my setup using Ansible and having those scripts versioned in Git, so I never have to worry about remembering how it’s all glued together.