Well, first, I would not be using DFMF, this is only used for special Enhanced Incremental Backups, and has caused more problems than it is worth
Having said that, the rest of your plan looks sound, whether you go with a physical server or a VM. One problem you may run into is with licensing. YOu need Advanced Backup to Disk license based on your Usable native capacity of a Data Protector file library is the available size on disk for the file library, as reported by the filesystem.
So, the Advanced Backup to disk license is based on the potential storage, not what was actually backed up
Adding another File Library of 2TB would require at least 2 1TB Advanced Backup to Disk licenses (Part # B7038AA)
Or, you could go into Devices and media, and delete the present storage location to use your current licensing, which, of course, would prevent you from doing a REstore once you get it back up and running
So, the theory is good, but, it may cost you some money