You seem pretty intimidated by us critics, don't worry, we're all doing this for fun anyway...
I like the basic concept of a harder nighttime event, but I disagree with some minor things. First of all, throughout your suggestion there's these mob "exceptions"- strays aren't affected by armors, creepers are weak to iron swords, witches spawn less. I think this just over complicates everything for the sake "balance". Of course the real balance for this suggestion is that's it's entirely optional- you could just sleep through it.
Secondly, eclipses happen too commonly. I'd change it to a 1% chance every night, so eclipses would theoretically happen once every 100 days or so. That way they could be rare and feel special.
The looting buff, if it had to remain, should be weaker and weaker as the difficulty progresses. I don't think the Ender Dragon advancement is necessary.
Finnally, I think the coolest part of eclispes is how it goes from the middle of the day to total darkness. Therefore, I'd suggest eclipses instead happen during the day, instead of the night. It would happen for only half the day, and you would be able to sleep through it. For example, you could be outside in the morning and notice that the moon hasn't left the sky yet. As it inches closer to the sun, you realize an eclipse is coming and gear up.
Despite all these criticisms, I think this is a good concept in general.
I agree with that also, having it happen 1% per night or day or whatever.