We lost the little one this morning. I think I thickened up the formula too much and possibly over-fed causing aspiration.

I know it happens and it's been a long time since I've done this.
I was able to get the male to feed the baby once in a four hour period. I fed the baby, two hours later, I gave the male some yogurt and candied carrots as a treat, and took him and the baby to the kitchen. It took a few minutes, but he ended up feeding the baby!! And the crop got full. This caused stress with the female (she was extremely irritated and was flapping around like crazy in the cage--not in the nesting box). I had been taking her into the kitchen so she could watch what I was doing. I put them both back, and in two hours, the baby had not been fed. I waited another half hour, but the female was not letting the father feed the baby--only her. I tried to replicate what I had done, but this time the father wanted to stay with the mother and would not go with me. So I did the hand feeding-- thickening the formula a bit more--I probably should have stayed with the consistency I was doing before. It didn't seem like it ate much and it's crop wasn't as big as in previous feedings so I tried to give it just a bit more and it seemed to bob and take it but some came out it's nose. I stopped and waited. It seemed okay after a few seconds. I still waited a bit and he was moving around as normal, didn't seem different than normal so I put him back with the parents and the mother immediately got him right under her wing. Two hours later he was gone. I'm not sure if anything else happened with the parents--if they were upset that I was feeding the baby.
The male is 3 and the mother is 2. I tried keeping them away from each other last year and that did not go over well. They became super-stressed and tried to get back to each other--often ending up on the ground or would hide together under the couch. Keeping them locked up seemed cruel. All I was told by people how to not keep them from mating is that I shouldn't have got a male and female. We had the male originally and the female (we didn't know until she laid eggs), was a gift from my father-in-law. I'm not really sure how to prevent the breeding. They certainly are quite the pair though. They are really stuck on one another. Do you have any suggestions?
So, far no other eggs have hatched. One doesn't look fertile. Two are dark. I couldn't check the other two that are left as the mother had enough of me prodding and wanted to sit on them.