Yes, but if you have a large amount of data then it may take up a good chunk of your hard drive space. SocialVault allows you to store these files online, and also provides a specialized file explorer for Facebook data.
So, you are competing with Google Drive?
Apparently not Nextcloud, since it doesn't seem you can self-host this.
Not really, Google Drive is centralized and google can always touch your data. But more importantly, if you dump your JSON file on Google, it will just be a JSON file. With SocialVault you can actually browse through the data in a meaningful way.