Yes, the whole dictionary is unarchived at the same time. You might want to create some wrapper and/or save each game state as 2 files (one for the metadata and one for the full state), possibly with each game in its own folder.
Putting archived data into a dictionary and then archiving the dictionary doesn't solve your initial problem and will take longer. The solution is to separate the 2 parts of data so they can be unarchived separately.