I'm not sure that was massively clearer!
The Freedom of the South West is valid from 9:00am, or whenever a Cheap Day Return is valid - whichever is earlier.
A Cheap Day return from Plymouth to Tiverton or Whimple is valid on the 8:55am train from Plymouth.
I don't know what the situation is if you change your mind and don't go through Tiverton or Whimple. I assume then that when you have changed your mind, you should buy a ticket for the original journey from Plymouth to Ivybridge (which may cause some confusion at the ticket office!).
You can get a ticket to Ivybridge rather than Totnes, the train doesn't actually have to stop at the station as you are combining a single ticket with a Rover.
BTW, the 'new' National Rail website seems to have completely messed-up the section on Rovers, and there is no information as to validity available at the moment.
It is refreshing to see that at least some people here do comply with T&Cs.
I am sure that the vast majority on here do comply with the T&Cs, as they are written - but where they are ambiguous, the consumer does have a statutory right to use the most favourable interpretation.