I also liked Glasgow a lot. I really enjoyed the Charles Rennie Mackintosh buildings I was able to track down. I made a side-trip to the attractive smaller town of Helensurgh to see the Hill House. This is easy enough by train if you decide to spend some time in Glasgow without a car. My trip was 26 days long and I spent six of those days in Glasgow; I enjoy cities, and I wasn't driving.
Relatively long stays are a good idea in Scotland since there's always a risk of rain (especially in the west); it's great to have some flexibility for each day's activities. With all that Scotland has to offer, I'm not sure I'd go as high as seven days on Skye, though. Four nights was too short, given the weather I ran into, so maybe five or six nights?? On the other hand, you'll have a car so if you got itchy feet you could drive off the island via the bridge at Kyle of Lochalsh to see things like Eilean Donan castle and the little village of Plockton.
Having no car, I used Oban as a base for the West Coast Motors trip to Mull and Iona. There's nothing terribly special about Oban; it's just convenient for folks depending on public transportation.
I used Dundee as a base to see St. Andrews. The Victoria & Albert Museum has a new branch, a design museum, in Dundee. The city has other museums and historic sights that might be of interest; it's blessedly non-touristy. On my way back to Edinburgh I took buses through some of the East Neuk villages rather than opting for the (faster) train.
There's a great deal more to see in Scotland. I'd recommend making full use of your car to see more of the Highlands than I did.
Many of the Scottish castles have nice, large gardens, making them not quick stops.
The tourism infrastructure in Scotland is somewhat underbuilt. There's more demand than supply where both lodgings and restaurant tables are concerned. Hotels in Dundee and Glasgow were comparatively inexpensive. Things were different in Oban, Portree and Edinburgh. You need to make dinner reservations if you expect to consume that meal sitting at a table in a restaurant as opposed to perching on a bench where you'll have to fend off the seagulls.