Hi and welcome to SevenForums,
Your backup script looks good - the only thing I would change is the "retry/time-out" option. If the user is using their laptop from home and is not connected to the network, and they then try run ROBOCOPY, it will by default attempt to reconnect up to 1 million times, with a 30 second wait time between reconnections - these are the default values.
A better option is to limit this to something like 3 retrys, with a 10 second wait time between each retry. In your example, it would look like this: (shown in red below)
r:3 = retry 3 times
w:10 = wait 10 seconds between each retry
To answer your other questions:
1. If the laptop is offsite and ROBOCOPY runs, then YES, it will fail gracefully and quickly - limiting the retry options will ease that failure too.
2. If they close the window, then they also close the ROBOCOPY function, and that will also fail gracefully and quickly.