You don't have to have LR write metadata to the dng files automatically and you probably shouldn't as there is a noticeable performance hit doing so. Instead, select the images and hit Command/Ctrl+S to save the metadata to the files once you are done editing them. ACR 4.1 will be able to then read the edits.
If you make edits in ACR, once back in LR make sure you synchronize the folder to update the catalog to reflect your new adjustments. "Library > Synchronize Folder..."
You can open virtual copies in PS but they have to be converted to an image file (non-raw) first. ACR 4.1 currently does not support virtual copies directly.
When you convert to DNG within LR, LR simply swaps out the old raw file for the DNG -- virtual copies remain virtual. When exporting files as DNG through the export window, LR will make a DNG for each file, including virtual copies -- virtual copies turn into actual copies.