That's a lot to read. my my. I don't even know where to start.
A little background info: I was born profoundly deaf and got implanted several months ago.
It's so hard to do the statistics of "happiness" of one having the CI. Are you asking if children grow up resenting having CIs or resenting how they are treated (like a hearing) BECAUSE they have CIs? Two very different things. I've noticed that the frustrations of a person who grew up with a CI is very similar to a HoH person. They both can hear a lot, but because they can hear a lot, people assume they can hear everything.
How can you determine if waiting to get a CI will harm the child if we can do fine without the CI? I did perfectly fine without the CI, however, I doubt my life would be WORSE with the CI. I can only see CI bringing benefits. You can only determine "harm" if you can magically see one's life with and without CI.
I don't know much about moderate/HoH people being candidates for the CI. I can tell you that I thought I heard okay with the HAs (relied a lot on lipreading), and didn't realize how much sound I was missing when I got the CI. Also, training to hear with the HA seems to me totally different from training to hear with the CI, at least for a born (or pre-lingually) deaf person because there are the adjustments that need to be done. With the HAs, it's highly likely that you will miss some sounds NO MATTER how loud it is. With the CI, most, if not all, sounds will be "heard", but adjustments need to be made THEN you have to learn the sounds. For example, recently I had AVT, and with the CI, I could NOT tell the difference between bee and baa, and with the HA, I can easily tell the difference (which means I "know" what they sound like), so my CI needs to be adjusted for that. However I can hear the t, p, s, sh very easily with the CI where I cant even hear them AT ALL with the HA. The HA's can only give you so much.
I'll stop for now!