The issue here is that Lemmy is federating out it's content with the pre blocks containing rendered code fit for some sort of code display plugin/CSS - which KBin doesn't have.
It would ideally send out the blocks html encoded and would let downstream implementations like KBin or others figure out how to display it themselves. I don't know how we would fix this.
This is actually due to the way these platforms work. When a user comments on a comment or post on their instance it will be shown on their instance. It's then sent on to the owning instance of that comment or post. That owning instance then forwards it on to all interested parties (magazine instance, commenters instance).
Any instance in that chain can refuse to forward or broadcast that message due to a block, but the users own instance will likely always show that post. Ideally they would not do that and would be made aware of a block but that is a bit of a grey area in ActivityPub implementations.
The issue with orchestration is that you still need a way to share those small databases and config files.
Docker has ok NFS support so you'd want to move the files to NAS shares and have them mount those. Without some way to centralise or spread the files out you won't be covering your SSD failure case. Once you've got that going docker swarm will probably cover your needs just fine.
You could go with K8S but based on you setup that's a bit overkill (unless you're doing it as a learning exercise, in which case go nuts).