Hi and welcome.
You vault (the encrypted vault files) is the folder “Vault” and all subfolders and files. Keep in mind that the folder “Vault” must not be a root folder. This is why you have to select an other root, and in your case this is the folder “CryptDir”.
unfortunately, there’s actually no way to upload folders. This will change as soon as the document provider feature is implemented (yes, it is announced since a long time, Im afraid there is no ETA so far.)
No. you can only look in your vault by using the cryptomator app. This will also change as soon as the document provider feature is implemented. Then your vault will be accessed via the file explorer on your phone.
Yes you can. In Your case copy the dir “Vault” and everything that is in it. I recommend to have an unencrypted, local backup of your files as well (no matter which encryption tool you are using)