Well his current age would be around 80 then, since hiruzen was 56 when he was made hokage again (after minato death), and as I've said before, Hiruzen was born after Konoha was founded, and I think hashi and madara were 25 when they founded it, at least if you look in databooks etc...
Itachi is not same age as Kakashi he is somewhat younger, I don't know how much but he is like 5 years older than Sasuke. He was 4 when he saw the causalities of war, which made him want to do anything to avoid it for the sake of Konoha and his brother. Also this was in the end of the war, so probably a year before sasuke/naruto was born, so he is 5 years older than sasuke.
Exactly, around his 80s. :y
In my Timeline, when he saved Obito, he was 84. :D