I've seen you do this on other threads. Is it a BYC feature? I'll get on the desktop and see if I can figure it out. Also, I did another egg and it looks like it died on day 17ish. I don't know why but it made me feel better! I guess like you said closure.
Trust me, if you use an incubator your face is glued to the window! So checking the nest box every 5 minutes would be totally normal! Just some advice on candling that far along, that helped me...was to shine the light into the air cell and just look for movement right around the base of the air cell. There won't be much to see throughout the egg because it will be filled with chick. But there's a small space where the inner membrane and air cell meet that you can sometimes see a little movement.