How to verify a self-encrypted drive (SED) is really encrypted?

One way to verify the drive is encrypted is to physically connect it to another machine. Either by direct SATA connection, or by a USB to SATA adapter. The other machine should be able to recognize the drive, but not be able to read the contents.

As for your second question, you most likely cant get it to "lock" the hard drive during a sleep. Even when a machine is sleeping, the OS is waiting in the background in a low power state. It has to be able to access and read the drive to come out of sleep.