VM snpashot is never recommended to restore DC.
Dcpromo /forcefull will forcefully remove the AD from the server but you will required to do the metadata cleanup from the other dc to remove the records of demoted dc.
The difference between dcpromo & dcpromo forcefull is dcpromo removes the AD gracefully & system will become domain member as well as it will wipe out the DC record from the AD after demotion but using forceful switch will make the server come out of domain & you have to manually do metadata cleanup to remove the entry.
I don't think it will work for public folder untill the PF database has been transferred to other exchange server it will generate error event.
You have to use the same hostname of the server to mount the database on exchange server if you manually move the database of exchange.
After moving all the mailbox along with public folder then only uninstall exchange server.
Well VM is not recommended but you can give a try.
I had similar task like exchange 2007,DC with FSMO,CA role but i gave a try & demoted the AD & everything worked fine.
The step i did is took backup of CA,AD as well as exchange database,stopped all the exchange service & then demoted the dc & after demotion i started the exchange service one by one & it worked...Give a try.
