I can usually see veins by day 3.I'm not completely sure. We brought this egg, along with a couple more that weren't fertile or died, in on 6/16. I could see a nice amount of veining that day so I was guessing it was at least 5 or 6 days along. Or are veins usually visible earlier than that? I remember thinking I could see a pulse in the veins but told myself I had to be imagining it because it seemed weird to see egg veins with a pulse. If my guess on day/age is close, I'd say he's around day 21 or 22 now.
I think since you aren't sure if stop turning the egg now.
I believe it is more important turn the eggs at the beginning of the incubation period. More so than towards the end.