When I should dare a guess, based on the previous tales ... in his mid forties. But this timeline has some 40 years between the fall of Citadel and Angrif's appearance in Recognition.
With the timeline confused like it seems to be (means the events and time marks in Wild Hunt are no longer reliable) there's no "well-founded" estimation for the recent story line.
The timeline that leads from the end of Shards directly via SatS/Discovery to TFQS counts about 26/27 years only. Angrif still looks like 40 for me - 5 years give or take.