Seems a bit high to me.

We know he has spent five years on the Cant and had a term on the Earth Navy that let him get into a relatively high position, weapons officer or exo given he refused an order from the captain to fire on a smuggler ship, and was spoke of highly by the UN Sec Gen so they had to be in the region of five to ten years. So he has to be something like 28-33 assuming he joined up at 18.

There is grey area on if he faced prison time after being court marshalled, of he joined the Canterbury straight away and he could age down in the other direction given he served in active duty chasing pirates and smugglers. I'd assume he could have been an exo in the navy in just a couple years.

So maybe the range could be as low as 26 and as high as 35?

The actor is 29 and by rule of thumb is any time their age isn't known the actors age is assumed correct. This hits the mid point of both ranges.