Thanks Bob.
I simply enabled vSAN on my cluster, was able to set up the storage successfully, passed all of the checks, then when I enabled stretched cluster and set up my two fault domains, I was able to add the witness with no errors either. So, I'm not sure why this is happening. Here's a few screen shots:
From Witness:
From Host 1:
From Host 2:
I've tried adding 3 different witness hosts, all of which were installed from scratch.
I'll get to work on trying some of your troubleshooting tips