Seeing that no one really knows, I decided to reformat my array with XFS to see if that, somehow, could be my NFS and CIFS issues. As for my CPU having some cores locked to 100% at times preventing me from doing any reboot or shutdown via ssh or the WebUI (I basically have to forcefully poweroff), someone who is runnning Unraid with docker told me it happened to him a few times so I am not alone experiencing these issues.
I'm giving this one more chance with my 12 days trial to see if somehow things hold up better. I'm more than willing to work with the developers if they want to get to the bottom of this but I need a running system and can't justify paying if I can't have a somewhat stable system.