Sure thing! This community has helped me immensely over the past year in my own installation, set up, and troubleshooting; happy to help when I can.
As far as the dual DCs; I am having the same problem myself. I tried the comma(,) and just a space and neither worked.
The field is labeled “Active Directory - Domains Controllers” with the “s” so I am thinking there should be a way of making it work, but would need the developers to weigh in on that one.
Best,
Dave