[IThoughtYouGNU]

Principal kubernetes consultant for a large firm here.

Kubernetes uses Docker runtime so that eliminates your first question. AWS also uses Kubernetes, EKS is a modified version of Kubernetes, and most major companies do not use things like Nomad because they lack the ecosystem tooling that something like Kubernetes has.

I think probably the best thing you could do to prevent issues like this is blue-green testing or proper integration testing with your infrastructure repository so you can roll back quickly when you realize that some change you made didn't work correctly. This is all in addition to significant amounts of it monitoring.