Predictions: After Brody is killed (perhaps Nazir may kill him before Estes), Carrie will reveal that Nazir had intel regarding the existence and location Walden's plastic case in his study at the Naval Observatory and used it to murder Walden That will lead to Saul, Peter and Carrie finding out who the mole is: Estes. He's close enough to Walden to know of his heart condition and I think Walden would confide in Estes the existence of the technology in the plastic case. Why would a terrorist mole order a drone attack? He may have ordered it along with Walden for a different reason than Walden's, to make the US look bad.
However, I'm not sure why Estes wanted Brody dead if they "got" Nazir and stopped his execution when he found out they didn't get Nazir. Perhaps, Nazir being alive, the plan to have Brody kill Walden would go forward, thus Estes "need" for Brody. If Nazir died, Estes could drop the plan to kill Walden, something he'd been conflicted about. Estes may want Brody dead to help ensure that his role as a mole remains a secret. Nazir may have threatened Estes to make him go along with his plan to kill the VP. Estes may have preferred staying close to a VP who might become the next President.
Someone wondered why the case was there and not at his doctor's office. I think there's more than one life saving box for the VP. There may be a doctor at the Naval Observatory who could quickly use the technology to save his life if there were a call for help.
I'll miss Damien Lewis, but I think Brody will die in episode 11. The mole will be revealed episode 12. Maybe Dar Adal will take Estes job. I hope I'm wrong!