If you can extend your stay another two weeks then I'd say your plans were feasable, but in seven days you're just not going to have the time to catch your breath before you're back on the plane heading home.

If you chose the longest days of the year and plan your journeys with military precision, flying into and out of Scotland - (I'd say try to find a chauffeur driven car so you dan be dropped off right outside major attractions and then picked up again, preferably with refreshments provided so you can eat in or beside the car) - and wear comfortable shoes/trainers and be sure to train up for the walking beforehand, then you might have a chance to cover all the mileage you envisage.