I am sorry to hear your attempt to save this little mouse ended so sadly. My name is Rebecca. I am a veterinarian and will do my best to help.
It is nearly impossible to save any baby this young. They need mouse milk; KMR and half and half would not have the correct balance of protein and fat for a mouse. In any baby this young, the right balance of ingredients in the milk is critical.
The watery yellow poop is probably the biggest clue to why she died. She was not blocked up from what you were feeding her, she had diarrhea and diarrhea in babies this young is almost always fatal. You did the exact right thing by giving the Pedialyte; extra fluids are what babies with diarrhea need. The only thing you may have done wrong was to over feed her; better too little food than too much in ones this young.
The clicking sound and the gasping could be signs she aspirated. Babies this young really need to suckle from a nipple and of course you could not get a nipple this small. But taking in drops by mouth, she could easily have aspirated some of the milk.
She may have had an infectious disease like Tyzzers and only an autopsy with specific tests for diseases would tell you, but it is more likely that she was doomed the moment she was parted from her mother. If she had been older, with fur and open eyes you might have been able to save her, but saving newborn anything, whether birds, kittens, puppies you lose more than you save. Their digestive tracts, immune systems and physiology are just so undeveloped that without a mother mouse, any slight imbalance was more than she could compensate for.
Another possibility that the mother knew something was wrong and abandoned her, as mothers of litters will do. She may have had a congenital problem the mother sensed, and rejected her because the mother knew she was not going to make it.
Thank you for your efforts to save her, and let me know if I can help with or answer anything else. Rebecca