Dar Adal is ruthless, but he does understand loyalty - he used Quinn's loyalty to the other soldiers in 'Group' to draw Quinn back into the CIA when he sent Quinn's teammate to the motel at the end of last season. Carrie ruled out Saul because he would have to be stupid to send Quinn to kill Carrie, Dar should be ruled out for the same reason.
Besides, whilst I do believe Dar would sacrifice his own people to achieve an important enough goal, I don't think Dar would give up an asset like Quinn lightly. He has always emphasised that Quinn is his guy, and at the start of the season he said 'I'm worried about Peter' after Quinn went off-script during the briefing. Presumably the hit was put onto Quinn to prevent Saul finding out who the Quinn's last target was, but as Dar is senior to Saul he didn't need Quinn killed to prevent that - if Quinn had gone through with the killing Dar could have either ordered Quinn to keep quiet about it or ordered Saul to accept it.
I think that the pills helped Carrie, but also the sedative Quinn gave her that probably made her sleep several hours. She has been off meds before - at the start of Season 3 before we knew of her pregnancy - and although she wasn't as together as she was at the start of this season she wasn't totally manic either. The first 3 days of the pills she may have kept a stable routine for the sake of Franny, but once the kid was gone she worked on an intense project for many hours and took stimulants instead of sleeping.
They cut back between Carrie and Allison a couple of times, so I believe that it was her at the other end. So I am convinced that she ordered the kills, although not necessarily that she is working for the Russians. The guy in the car wasn't given the job of tracking and killing Carrie himself so may not be a highly trained spy. Allison needed him for simpler task of sitting at one location and shooting the target when he comes by - it might be that the only hitman she knew how to hire without using CIA resources happens to be Russian.
