Hey Todd -
First, we should probably get this out of the way. Here is some guidance on splitting an 8 core. Give it a quick glance?
Got it? Don't do what you're doing . I assume this is just a science experiment on your part, however....
Now, to your problem. As I recall (and things may have changed), you cannot do a distributed deployment of Tableau Server with a trial key. In years gone by, there was actually a message that would say (essentially) "You can't to that". Can you confirm you are using a trial key?
You've covered all the other bases nicely - connectivity is there, name resolution APPEARS to be there, no firewall. Good stuff. The only other thing I could offer is to use IP addresses when you plug in the worker names INSTEAD of dns hostnames. I've occasionally seen a ping against a hostname work but postgres still end up getting confused.
I haven't done much trial installations of Tableau Server, can someone from Tableau confirm that distributed install on trial license is not allowed?
As for troubleshooting, I would reinstall worker software and enter the primary's server's static IP instead of DNS name when prompted.