1- Traffic is not the primary problem with driving in Ankara. All the sites you want to see have parking, so that won't be a problem either.
The evil mayor has all the roads (yes, all of them except a few very large ones) in Çankaya district (includes Kızılay Sq., Kocatepe Mosque, Tunalı Hilmi and Atakule) be one-way, as revenge for Çankaya not voting for him :) This turns southern Ankara into a giant labyrinth. I don't know if GPS's have all the one-way directions in them.
Taxis are cheap, and it will probably cost 10$ between the farthest two of your destinations.
4- Atakule Tower and walls of the Citadel both offer nice views of the city, but Citadel is better in my opinion, as it is more central. Still, I think the revolving restaurant is worthwhile, as it is something you don't get to do often. It has the menu items of a regular Turkish restaurant (various grill plates, a couple of soups, salads, appetizers, desserts) and the food is ok. The prices are as any other restaurant of its class (expect 15$ per person).
Other restaurant suggestions are:
Göksu (at the corner of Nenehatun and Tahran Avenues) is a gigantic restaurant with a very formal setting (but no dress code is imposed);
Uludağ (if you haven't had İskender Kebap yet, this is the place to have it) which has several branches, oldest being in the old town near the citadel - perhaps a good place for your lunch before or after going to the Citadel;
Cafemiz (continue uphill from the Kuğulu Park end of Tunalı Hilmi Ave, past Sheraton, and you'll find it on the left on Arjantin Ave.) is a cute and cozy restaurant with modern food, and is frequented by foreigners.
Merkez Lokantası (a few km from the city center, near the zoo) has the distinction of being the oldest restaurant of Ankara, frequented by Ataturk and other founders of Turkey. It serves excellent food. It basically is a regular Turkish restaurant with a much extended menu. It has a large garden so you can eat outside among trees.
5- Prettiest roads are in Çankaya district, because they are lush with trees. I particularly like the part of Ataturk Boulevard between Kızılay and Akay. Akay is 800m south (uphill) from Kızılay, and that is where the parliament is.
From Akay, the boulevard continues south for 3 km up towards Atakule tower. At about the middle of this 3km is Kuğulu Park, which is the intersection to Tunalı Hilmi Ave. The park itself is very small but pretty. Sheraton is a nearby piece of architecture, with its wine bottle-inspired shape and 2-floor windows that gives it the illusion of smallness.
From Akay, if you go 3.5 km west, you'll notce Armada Tower, with its naval-inspired architecture. Just before that is an intersection where you can turn south (following signs pointing at Konya) for the Tuz Lake route. This route has several modern buildings, but is busy like a motorway, so it is slightly difficult to stop for taking pics.
The most beautiful place for modern architecture is the residential Dikmen Valley. It stretches in the north-south direction, less than 1 km west of Atakule. For a landmark, it has two pairs of pink residential 140m tall towers.
6- Kocatepe Mosque is larger than any in Istanbul, and has a pretty 1-ton chandelier. But yes, it is made in standard Ottoman architecture. So I'd say take a look if you have time.
7- There are two routes: It is a tiny bit shorter through Kırşehir, but it seems people like views of the one near Tuz Lake better. I don't think you'll have any problem, even in the dark, because both of these roads are divided (2x2 lanes). It is not far in any case.