Sorry that it didn't make it. I've become quite experienced at assisted hatching thanks to my crossbred turkeys, but even so I lose some with too early or too late an assist, or with moisture control. I used to advocate using a moist paper towel around the shell to help retain moisture but I found that in a forced air incubator, this causes a chilling effect that can also kill the chick. I do think the inner membrane may have dried a bit overmuch after the shell was breached, and for that, so long as there is an internal pip, I use a petroleum based antibiotic ointment and swab it on the membrane. It will preserve the existing moisture nicely. I don't know why that chick had such prominent blood vessels at that time and stage. I am sorry for the loss of the chick but as you said, you do gain new insight and perhaps the next time you have a challenged one you'll have a better outcome.