Well, his real age can be counted in millenniums and beyond due to reality warping shenanigans. His body, however, is really that of a sixteen year old. It's not stated exactly how long said reality warping shenanigans has been going on so it's impossible to give an accurate age for him.

As for his Precognition, it won't really come up in most threads. Think of as a "Warrior's Instinct" that's limited to supernatural attacks. The only information it gives him is that he's going to die horribly if he doesn't defend himself. It doesn't tell him anything about what the attack is or what it does. Also, it's not perfect and Touma is still only as fast as a normal human. Dealing with multiple attacks at once isn't exactly a cakewalk when you're sole defense is your right hand.

If I need to, I can also just talk it out with the other player.