Help with 6 day road trip

Goodness you will be seeing the Highlands through a car windscreen! 31st July is particularly jam packed. Getting the 1255 or 1420 ferry from Mallaig will give you only 1 afternoon on what is one of Scotland's largest islands. You won't be able to really experience the island at all in that time. You might make it to the fairy pools along with hundreds of other visitors but you won't get a true feel for the more remote (and beautiful) areas. Basically you will be just be driving from one part of Scotland to the next each day. I'd have a serious rethink and maybe concentrate your precious time on one area closer to Glasgow (e.g. Isle of Aran or maybe Mull). It's hard to advise in more detail without knowing what in particular you hope/want to see, i.e. what is the main focus of your visit.

That is a lot of driving, particularly if you are the only driver...

Don't undwerestimate driving times. If using Google maps add 25% to their times and then add on time for any stops. Driving in Scotland is very different to New Zealand and in places will be a lot busier...One night stops are also hard work.

Day 2 is daft and is very much short changing Skye. . You have to catch a ferry from Mallaig to Armadale. The summer timetable for the ferry isn't out yet, so you will need to check sailing times as soon as it is available. Although its not far to drive from Armadale across Skye and over the bridge for Plockton, you need to allow 60min+ for the drive (PLUS any stops on the way). You are also missing many of the prettiest parts of Skye too.

Is Skye a Must see? Have you thought about Mull instead, reached by ferry from Oban? There is less driving and could be reached on day 1. Plan to spend 2 nights there. This is the bare minimum but will allow you to spend a full day on the island. Tobermory is a lovely small town.
On Day 3 head to Anstruther via Pitlochry and then spend 2 nights there.
Day 5 head to Stirling