So question is: What actuality happens if Armory is used and wallet deleted from after use by pressing Delete/Remove Wallet button on the Wallet Properties screen?
The wallet file will be deleted and you will need the wallet's root key or your private key(s) to have access to your bitcoin.
Can this deleted wallet file be somehow restored and keys recovered and bitcoins get stolen?
It's possible that files are that have been deleted from your device can be restored using a data recovery tool. So, the wallet file hasn't permanently gone.