What was Uriyah's answer?
Malbim: I cannot eat and drink and be intimate with my wife, for (a) The Aron is in a hut (not in its place) 1 . (b) The soldiers are in huts and the officers are on the fields, suffering from heat during the day and cold at night.
Eruvin 63b: A tradition teaches that when the Aron and Shechinah are not in their place, intimacy is forbidden. Malbim citing Mahari - that applies only to the Aron that houses the Luchos. The Aron with Yo'av had the Efod and Urim v'Tumim.
Was he allowed to say "Adoni Yo'av"?
Rashi (Kidushin 43a): This is Mored b'Malchus, to call Yo'av his master in front of the king! Malbim - this implies that Yo'av is primary (more than David). The Teku'is (14:19) said "Avdecha Yo'av."
Tosfos (Kidushin 43a): This was not rebellion, for Yo'av was not rebelling against David. The Gemara says that Uriyah rebelled, for he disobeyed David's command, or because he mentioned Yo'av before mentioning David.
Why did he say "Chayecha v'Chayei Nafshecha"?
Radak: [It is as if he swore by] your life in this world, and your life in the world to come.
