What is the age of this 6 point buck?

2.5

2

yeap he's just 2.5

2 no doubt

Yup, 2 (add the 1/2 half if you want to shoot him)

Doesn't he have quite a gut to be only 2.5?

No it is a normal gut for a young deer in a year like we have had. The deer have eaten good this year.
Look at his lower neck and brisket area, long and skinny, small head and bottle nose, light color tassel glands.
2.5 years old.

His gut is a side effect of how he is standing or moving at the time of the pic.

I dont see much of a gut regardless. He's 2.