1. I think immediately: ah-YA-kah. I think that's how it would be more accurately pronounced in Japanese.
2. I prefer
Ayaka for some reason over Ayeka, but both look OK.
3. I'm not sure whether you'd like Japanese mn to go with this one, so I'm going to suggest a mixture:
Ayaka CamilleAyaka CelesteAyaka ChoAyaka ClaireAyaka DaphneAyaka JaneAyaka JulieAyaka LillianAyaka MeiAyaka Olive /
OliviaAyaka ReiAyaka Robin
4. That's really a matter of personal opinion, isn't it? Personally, I'd like to see it with other Japanese names, but that's just me.
5. It's quite a pretty name, but nms.