1. if your transaction is confirmed in any block after 478558 and if their replay protection worked then yes you still have 0.27 BCC waiting to be claimed.
2. the wallet that used to contain your 0.27BTC and remember to not use that wallet ever again.
3. see their website and don't trust the binaries much. and install them on a separate computer if you want to be safe.
Thank you for your input. I currently do not have a smartphone nor a second computer. One thing I can do, however, is wipe the hard drive (there's almost nothing on this computer anyway) and create a second wallet. This brings up a fourth question: can Bitcoin Cash wallets be backed up and saved onto a USB drive?