The red ring does not always mean the ring of death!! I personally don't throw anything away until at least day 14 of candling. I mark unsure eggs and leave them I smell the incubator often for bad smells and if something smells dodgy I will check my unsure eggs. I only candle day 7, 14 and 18...
Hi :welcome
Glad you joined the flock. Your right high temperatures are more likely to kill an embryo than cool temperatures. But don't give up hope yet, your red spider web you described sounds to me like normal veining developing in the early stages of incubation...