Hi there
You don't say exactly when you are coming to Scotland, and that might have an impact in terms of daylight hours and how much you will be able to do in a day. I'm also going to assume that you have arranged a rental car and that you have already booked your accommodation as your overnight locations are very specific. Having made those assumptions here are my thoughts;
Where are you collecting your rental car? If in the centre of Edinburgh you will find driving in the city and traffic problematic. There are many bus/taxi lanes and traffic is generally highly congested. You would probably be best to collect your car at Edinburgh airport after you have finished exploring the city.
Dalhousie castle is well south of Edinburgh, but you are then proposing to head north the next day. From your accommodation to Stirling castle will take at least an hour and probably more in traffic (rush hour traffic around Edinburgh is very heavy). You will need a full morning to do justice to Stirling castle, and then it will take you about 1.5 hours to get to PItlochry. The next 3 sites that you want to see on that day, the Falls of Foyers, Urquhart Castle and Loch Ness are however, not on the way to your accommodation, but would be better dealt with on your way to Skye. Unless you have a particular reason for wanting to stay in Evanton overnight it does seem a strange choice of location. Have you thought about where you'd have dinner? I don't know the village but it looks tiny on the map and is a good ways north of Inverness. Personally, I would reconsider that one.
Your day 3 plans are OK, you can see Loch Ness etc en route to Skye and the route also takes you past Eilean Donan castle (in my opinion not worth going inside, but lovely from the outside). From Evanton to Eilean Donan would take you about 2.5 hours without any stops, but obviously if you want to stop around the Loch Ness area (Urquhart castle etc) then you are adding another couple of hours, so I suggest getting an early start and aiming to be crossing the bridge onto Skye just after lunch. This would give you time for a whistlestop look at the Trotternish peninsula to see the Old Man of Storr, Kilt Rock etc.) and then find your B&B which is near Staffin. Again I would ask whether you have thought about dinner that night, as options are very limited around that area. You'd probably be heading over to Uig for the Ferry Inn, or down into Portree. You will definitely need to make dinner reservations on Skye if you are coming anytime between May and the end of September.
On day 4 you ask what else you can see on Skye, but my question would be where in Argyll and Bute (a large region) is your accommodation? I assume you are planning on heading down through Glencoe? Are you planning to take the ferry off Skye from Armadale to Mallaig? This would give you the opportunity to see different scenery than on your arrival journey. If so you need to make reservations ahead of time. Depending on where you are trying to get to and which ferry you get then you might not have much time to see much more of Skye as from your accommodation to Armadale ferry terminal will take you close to 2 hours (with tourist traffic - I assume you won't over take as much as I do, and it would take me at least 1 hour 45 minutes). So I think you need to think about this day in more detail before we can help with other sites on Skye.
Day 5 to Glasgow. I am not a resident of Glasgow and don't go there that often, but I was under the impression that the Guinness brewery and tour was in Dublin not Scotland? If there's nothing else to detain you in Glasgow, then personally I'd add another night in the Highlands or on Skye as at the moment your itinerary is super busy and it seems like a heck of a lot of driving for not that much sight seeing.
Hope this helps. Jacqui (Skyegirl)
