The initial humidity sound maybe a little high but that wouldn't stop eggs from developing at all. Temp seems right if taken at the eggs. Your incubator is very much like mine in overall design but my heat design is a little different.
If there are no blood rings, and no signs of growth, that can mean: infertile eggs, something happened to the eggs before incubation started (like freezing or deep chilling), or that something drastic happened in the incubator in the first three days, like a major heat spike. That's too soon for infection to kill them, unless the eggs were washed. If you candle at 7 days and crack the clears, there is no sign of development?
I wouldn't use the sponge except maybe for lockdown. They harbor bacteria. The water in that tray looks a little off color.
Are you saying that if you take eggs that were started by a broody, you can finish the incubation successfully inside?
Sorry about all the questions, but questions lead to answers, which it seems you are looking for.