Last year there was no initial deposit that had to be sent with the acceptance postcard- you just send in the postcard. (It is possible this has changed for this year, but I doubt it- unless it specifically tells you to send in a deposit with the postcard, you don't have to.)
1. Sorry, I don't know about that.
3. Yes- the T connects Harvard to both.
From South Station, you'd take the Red Line inbound six stops to get to Harvard. From Logan airport, you could take the Silver Line (which is a bus) to South Station (then take the Red Line the same way).
Both trips would cost two dollars.