Need feedbacks on driving itinerary

You've got a lot of destinations and activities mapped out. This could work, because geographically it is pretty logical, but it will require a lot of energy with no pauses for, say, laundry or just chilling out one day. On the positive side, most of your overnight stays are at least 2 nights in a given location, which will increase your chances of being reasonably well rested.

I would just suggest you try to be flexible and think of which activities are optional in case you get tired or run short on time. For example, it's certainly possible to see Culloden Battlefield, Clava Cairns, and Cawdor Castle in one day, but which of those would you skip if necessary? Toward the end of the trip you might decide you like St. Andrews so much that you'll forgo Stirling Castle, or conversely that Stirling Castle interests you more than driving all the way over to St. Andrews.

Thank you epltd for your applicable feedback! We will consider choosing one destination over the other ahead of our trip.

Our only concern now is:
1) on Day 6 - whether we can make it to the Skye ferry terminal 30min before the ferry departs. So we have been thinking of staying somewhere between Oban and Mallaig for 1 night? Has anybody done the driving route from Oban via the Skye ferry and make it to Portree in early evening?
2) OR should we drive up to use the Skye Bridge instead of taking the Skye ferry as “sailing can be canceled in rough weather” (quoted from RS's guidebook on Scotland). I heard that weather in Scotland is unpredictable, would the cancellation be a possibility for travel in June?
We would prefer to keep our original plan because in changing to either 1 or 2, we have to disarrange the booked accommodations in the days before and following.
Need help!

Have you considered an over-night in Ft. William? We're visiting in May and do not have a car, so we don't have the flexibility you will have but we've decided on a stay at Ft William as we travel from Mallaig (actually Portree) to Oban. While we understand Ft. William is not a destination, per se, (our upcoming visit will be our first), but Neptune's Staircase, the West Highland Museum, Lochaber Archive Center and Glen Nevis appear to us to be good venues to visit. While we're too old, in years past we would have enjoyed taking the gondola to the Nevis Ski Area and then taking a mountain bike down. Also, if one of your party would be the "designated driver" to Mallaig, the others could ride the Jacobite Steam Train.

As noted above, we're newbies regarding Scotland and can't speak from experience, but the Day 13 drive from Doune to St. Andrews to Stirling Castle and back to Doune seems like backtracking; particularly if you're driving to Edinburgh the next day. Have you thought about an over-night in Stirling or Falkirk and perhaps visit the Battle of Bannockburn Center, the Falkirk Wheel and/or the Kelpies at the Helix? Then on to Edinburgh.

Thank you Jon for your thoughtful input.

Fort William is the town on our way to Mallaig. However we find it too close to Oban to worth an overnight stay. Besides, we just checked that the change will not allow us to visit the places of interest in our schedule. Thus we will play it by ear if we have to cut short of some sights so we can get to Portree on Day 6.
You are right about the backtracking. We will consider staying in Falkirk instead.
Thanks!